Relax restriction on suffix of apex_set filename to include .capex

Compressed APEX files generated by the build system have the .capex
extension. This CL allows us using those .capex files with their actual
suffix.

Bug: 197258691
Test: manual + unit test added
Change-Id: I79173ef942326b48b5e659f1873d80f12b212339
diff --git a/apex/prebuilt.go b/apex/prebuilt.go
index 1bb0fb5..c4794dc 100644
--- a/apex/prebuilt.go
+++ b/apex/prebuilt.go
@@ -924,8 +924,8 @@
 
 func (a *ApexSet) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 	a.installFilename = a.InstallFilename()
-	if !strings.HasSuffix(a.installFilename, imageApexSuffix) {
-		ctx.ModuleErrorf("filename should end in %s for apex_set", imageApexSuffix)
+	if !strings.HasSuffix(a.installFilename, imageApexSuffix) && !strings.HasSuffix(a.installFilename, imageCapexSuffix) {
+		ctx.ModuleErrorf("filename should end in %s or %s for apex_set", imageApexSuffix, imageCapexSuffix)
 	}
 
 	inputApex := android.OptionalPathForModuleSrc(ctx, a.prebuiltCommonProperties.Selected_apex).Path()