Treat "apex" system_ext the same as platform

Change https://r.android.com/1672245 added support to treat
system_ext:foo in the boot jars configuration the same as platform:foo,
at least for dexpreopt_bootjars.go's getBootJar.

This change replicates that mechanism in platform_bootclasspath and as
that now handles hidden API processing also made a similar change in
the isModuleInConfiguredList function.

Bug: 177892522
Bug: 154976937
Test: m nothing
Change-Id: I105f4fbaa3b0355b013b7c5618d218d888faefb6

java/platform_bootclasspath_test.go

@@ -33,7 +33,7 @@ var prepareForTestWithPlatformBootclasspath = android.GroupFixturePreparers(
 func TestPlatformBootclasspath(t *testing.T) {
 	preparer := android.GroupFixturePreparers(
 		prepareForTestWithPlatformBootclasspath,
-		FixtureConfigureBootJars("platform:foo", "platform:bar"),
+		FixtureConfigureBootJars("platform:foo", "system_ext:bar"),
 		android.FixtureWithRootAndroidBp(`
 			platform_bootclasspath {
 				name: "platform-bootclasspath",
@@ -45,6 +45,7 @@ func TestPlatformBootclasspath(t *testing.T) {
 				system_modules: "none",
 				sdk_version: "none",
 				compile_dex: true,
+				system_ext_specific: true,
 			}
 		`),
 	)