Notice files for prebuilt_etc are included in APEX

This change fixes a bug that notice files for some module type (e.g.
prebuilt_etc) were not included in APEX. This happened because we relied
on WalkPayloadDeps which actually doesn't traverse module types that
don't implement ApexModule interface. prebuilt_etc is one such module
type. Fixing the problem by also iterating the filesInfo array which
has info about all modules that are included in the APEX.

Bug: 166575301
Test: m com.android.tzdata and inspect the built artifact.
NOTICE.html.gz is there.

Change-Id: Iceb055b60184aef2a3e65e44680304853eb79a53

apex/apex.go

@@ -1189,6 +1189,8 @@ type apexFile struct {
 	overriddenPackageName   string           // only for apps
 
 	isJniLib bool
+
+	noticeFiles android.Paths
 }
 
 func newApexFile(ctx android.BaseModuleContext, builtFile android.Path, androidMkModuleName string, installDir string, class apexFileClass, module android.Module) apexFile {
@@ -1204,6 +1206,7 @@ func newApexFile(ctx android.BaseModuleContext, builtFile android.Path, androidM
 		ret.requiredModuleNames = module.RequiredModuleNames()
 		ret.targetRequiredModuleNames = module.TargetRequiredModuleNames()
 		ret.hostRequiredModuleNames = module.HostRequiredModuleNames()
+		ret.noticeFiles = module.NoticeFiles()
 	}
 	return ret
 }