Remove App Engine build/environment scripts (#2870)

It's been over half a year now since we last used any of these and we definitely
no longer have any intentions of ever using App Engine again.

BUG= http://b/457471639

Author: CydeWeys

.gitignore

@@ -121,9 +121,5 @@ core/**/registrar_dbg*.js
 core/**/registrar_bin*.css
 core/**/registrar_dbg*.css
 
-# Appengine generated files
-core/WEB-INF/appengine-generated/*.bin
-core/WEB-INF/appengine-generated/*.xml
-
 # jEnv
 .java-version

appengine_war.gradle

@@ -331,9 +331,6 @@ subprojects {
 
   // Set up all of the deployment projects.
   if (services.contains(project.path)) {
-
-    apply from: "${rootDir.path}/appengine_war.gradle"
-
     // Return early, do not apply the settings below.
     return
   }
@@ -380,17 +377,6 @@ subprojects {
   }
 }
 
-// Force SDK download and deployment to be sequential, otherwise parallel tasks
-// will fail. For SDK download, they will try to write to the same location to
-// upgrade gcloud. For deployment, they will try to deploy different services to
-// the same project at the same time.
-for (int i = 1; i < services.size(); i++) {
-  project("${services[i]}").downloadCloudSdk
-          .dependsOn(project("${services[i - 1]}").downloadCloudSdk)
-  project("${services[i]}").appengineDeployAll
-          .dependsOn(project("${services[i - 1]}").appengineDeployAll)
-}
-
 // If "-P verboseTestOutput=true" is passed in, configure all subprojects to dump all of their
 // output and final test status (pass/fail, errors) for each test class.
 //