test: a tweak to fix a test failure

These changes fix a test failure that happened in my dev environment.

They make sure to use a directory created by @tempdir, rather than just
using java.io.tmpdir (a very full/messy tmp directory was causing one of
the config tests to fail).

Also, a new .gitignore hides the intellij download created for tests in
agent/test/intellij.

Author: apotterri

agent/src/test/java/com/appland/appmap/config/AppMapConfigTest.java

@@ -37,7 +37,7 @@ public void loadBadDirectory() throws Exception {
     public void createDefault() throws IOException {
         // Just verify that the file gets created when it should. The contents
         // get verified elsewhere.
-        Path configFile = Paths.get(System.getProperty("java.io.tmpdir"), "appmap.yml");
+        Path configFile = tmpdir.resolve("appmap.yml");
         Files.deleteIfExists(configFile);
         AppMapConfig.load(configFile, false);
         assertTrue(Files.exists(configFile));
@@ -55,7 +55,7 @@ public void preservesExisting() throws IOException {
 
     @Test
     public void requiresExisting() throws Exception {
-        Path configFile = Paths.get(System.getProperty("java.io.tmpdir"), "appmap.yml");
+        Path configFile = tmpdir.resolve("appmap.yml");
         Files.deleteIfExists(configFile);
 
         String actualErr = tapSystemErr(() -> AppMapConfig.load(configFile, true));

agent/test/intellij/.gitignore

@@ -0,0 +1 @@
+appmap-intellij-plugin