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
diff --git a/java/hiddenapi_singleton.go b/java/hiddenapi_singleton.go
index 3cc88e6..9826baf 100644
--- a/java/hiddenapi_singleton.go
+++ b/java/hiddenapi_singleton.go
@@ -186,7 +186,7 @@
 
 	// Now match the apex part of the boot image configuration.
 	requiredApex := configuredBootJars.Apex(index)
-	if requiredApex == "platform" {
+	if requiredApex == "platform" || requiredApex == "system_ext" {
 		if len(apexInfo.InApexes) != 0 {
 			// A platform variant is required but this is for an apex so ignore it.
 			return false