Make apex tests parallel

Mark all the apex tests and subtests with t.Parallel(), which will allow
the test runner to run them in parallel.  Reduces the time required to
run the apex tests from 70s to 9.7s.

Test: go test ./apex
Flag: EXEMPT test only
Change-Id: I08bd3cb4d8eec1f9520c1118b4525aa79e95288e
diff --git a/apex/aconfig_test.go b/apex/aconfig_test.go
index bb811f5..2ab61b3 100644
--- a/apex/aconfig_test.go
+++ b/apex/aconfig_test.go
@@ -33,6 +33,7 @@
 })
 
 func TestValidationAcrossContainersExportedPass(t *testing.T) {
+	t.Parallel()
 	testCases := []struct {
 		name string
 		bp   string
@@ -294,6 +295,7 @@
 	}
 	for _, test := range testCases {
 		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
 			android.GroupFixturePreparers(
 				java.PrepareForTestWithJavaDefaultModules,
 				cc.PrepareForTestWithCcBuildComponents,
@@ -309,6 +311,7 @@
 }
 
 func TestValidationAcrossContainersNotExportedFail(t *testing.T) {
+	t.Parallel()
 	testCases := []struct {
 		name          string
 		expectedError string
@@ -709,6 +712,7 @@
 	}
 	for _, test := range testCases {
 		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
 			errorHandler := android.FixtureExpectsNoErrors
 			if test.expectedError != "" {
 				errorHandler = android.FixtureExpectsAtLeastOneErrorMatchingPattern(test.expectedError)
@@ -730,6 +734,7 @@
 }
 
 func TestValidationNotPropagateAcrossShared(t *testing.T) {
+	t.Parallel()
 	testCases := []struct {
 		name string
 		bp   string
@@ -786,6 +791,7 @@
 	}
 	for _, test := range testCases {
 		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
 			android.GroupFixturePreparers(
 				java.PrepareForTestWithJavaDefaultModules,
 				cc.PrepareForTestWithCcBuildComponents,