Make LocalDatastoreHelper aware of --use-firestore-in-datastore-mode

[ablx]

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Is your feature request related to a problem? Please describe.
I am using Firestore in Datastore mode, yet I cannot correctly emulate it in unit tests since I cannot configure --use-firestore-in-datastore-mode

Describe the solution you'd like
LocalDataStoreHelper should have the possibility to hand over the --use-firestore-in-datastore-mode parameter to the emulator.

Describe alternatives you've considered
Using Testcontainers

Additional context
GoogleCloudPlatform/spring-cloud-gcp#1406

[ablx]

I started to implement it: https://github.com/ablx/java-datastore/tree/949_localdatastorehelper_firestore_in_datastore_mode

However, it does not work. The emulator does not seem to start correctly. If I use the generated prompt directly with gcloud, it works. I cannot see any error logs from the emulator other than below; which is not helpful.

Maybe someone can give me a hint.

com.google.cloud.datastore.DatastoreException: I/O error

	at com.google.cloud.datastore.spi.v1.HttpDatastoreRpc.translate(HttpDatastoreRpc.java:140)
	at com.google.cloud.datastore.spi.v1.HttpDatastoreRpc.commit(HttpDatastoreRpc.java:166)
	at com.google.cloud.datastore.DatastoreImpl$5.call(DatastoreImpl.java:583)
	at com.google.cloud.datastore.DatastoreImpl$5.call(DatastoreImpl.java:580)
	at com.google.api.gax.retrying.DirectRetryingExecutor.submit(DirectRetryingExecutor.java:103)
	at com.google.cloud.RetryHelper.run(RetryHelper.java:76)
	at com.google.cloud.RetryHelper.runWithRetries(RetryHelper.java:50)
	at com.google.cloud.datastore.DatastoreImpl.commit(DatastoreImpl.java:579)
	at com.google.cloud.datastore.DatastoreImpl.commitMutation(DatastoreImpl.java:572)
	at com.google.cloud.datastore.DatastoreImpl.put(DatastoreImpl.java:532)
	at com.google.cloud.datastore.DatastoreHelper.put(DatastoreHelper.java:53)
	at com.google.cloud.datastore.DatastoreImpl.put(DatastoreImpl.java:507)
	at com.google.cloud.datastore.testing.ITLocalDatastoreHelperTest.testCreateWithFirestoreInDatastoreMode(ITLocalDatastoreHelperTest.java:110)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:568)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38)
	at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
Caused by: com.google.datastore.v1.client.DatastoreException: I/O error, code=UNAVAILABLE
	at com.google.datastore.v1.client.RemoteRpc.makeException(RemoteRpc.java:171)
	at com.google.datastore.v1.client.RemoteRpc.call(RemoteRpc.java:117)
	at com.google.datastore.v1.client.Datastore.commit(Datastore.java:87)
	at com.google.cloud.datastore.spi.v1.HttpDatastoreRpc.commit(HttpDatastoreRpc.java:164)
	... 40 more
Caused by: java.net.ConnectException: Connection refused
	at java.base/sun.nio.ch.Net.pollConnect(Native Method)
	at java.base/sun.nio.ch.Net.pollConnectNow(Net.java:672)
	at java.base/sun.nio.ch.NioSocketImpl.timedFinishConnect(NioSocketImpl.java:542)
	at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.java:597)
	at java.base/java.net.Socket.connect(Socket.java:633)
	at java.base/sun.net.NetworkClient.doConnect(NetworkClient.java:178)
	at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:498)
	at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:603)
	at java.base/sun.net.www.http.HttpClient.<init>(HttpClient.java:246)
	at java.base/sun.net.www.http.HttpClient.New(HttpClient.java:351)
	at java.base/sun.net.www.http.HttpClient.New(HttpClient.java:373)
	at java.base/sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1309)
	at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1242)
	at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1128)
	at java.base/sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:1057)
	at java.base/sun.net.www.protocol.http.HttpURLConnection.getOutputStream0(HttpURLConnection.java:1430)
	at java.base/sun.net.www.protocol.http.HttpURLConnection.getOutputStream(HttpURLConnection.java:1401)
	at com.google.api.client.http.javanet.NetHttpRequest.execute(NetHttpRequest.java:113)
	at com.google.api.client.http.javanet.NetHttpRequest.execute(NetHttpRequest.java:84)
	at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:1012)
	at com.google.datastore.v1.client.RemoteRpc.call(RemoteRpc.java:97)
	... 42 more

[cindy-peng]

The above error is caused by a outdated version of cloud emulator 2.0.2. However there are some challenges updating cloud emulator to the latest version 2.3.1 since the new cloud emulator doesn't support Java 8. Submitted this PR for the fix: #1698.