Don't create a new module for bp2build conversion.

A performance improvement for bp2build as Blueprint/Soong no longer have
the overhead of additional modules. The creation of these modules
results in:
* traversal of additional modules for each subsequent mutator
* synchronization over a go channel to collect newly created modules:
https://cs.android.com/android/platform/superproject/+/master:build/blueprint/context.go;l=2594,2600;drc=1602226f23181b8c3fbfcaf3358f0297e839d7d3

We avoid both of these by storing the information directly in the
underlying module.

Also as a fringe benefit, removes some necessary boilerplate for
conversion.

For benchmarks, reduces runtime ~1% for 1% converted, ~24% for 100%
converted. See more: go/benchmarks-for-https:-r.android.com-1792714

Test: ran benchmarks/tests in bp2build
Test: build/bazel/ci/bp2build.sh
Change-Id: Ie9273b8cbab5bc6edac1728067ce184382feb211

etc/prebuilt_etc.go

@@ -662,18 +662,6 @@ type bazelPrebuiltEtcAttributes struct {
 	Installable bazel.BoolAttribute
 }
 
-type bazelPrebuiltEtc struct {
-	android.BazelTargetModuleBase
-	bazelPrebuiltEtcAttributes
-}
-
-func BazelPrebuiltEtcFactory() android.Module {
-	module := &bazelPrebuiltEtc{}
-	module.AddProperties(&module.bazelPrebuiltEtcAttributes)
-	android.InitBazelTargetModule(module)
-	return module
-}
-
 func PrebuiltEtcBp2Build(ctx android.TopDownMutatorContext) {
 	module, ok := ctx.Module().(*PrebuiltEtc)
 	if !ok {
@@ -723,11 +711,5 @@ func prebuiltEtcBp2BuildInternal(ctx android.TopDownMutatorContext, module *Preb
 		Bzl_load_location: "//build/bazel/rules:prebuilt_etc.bzl",
 	}
 
-	ctx.CreateBazelTargetModule(BazelPrebuiltEtcFactory, module.Name(), props, attrs)
+	ctx.CreateBazelTargetModule(module.Name(), props, attrs)
 }
-
-func (m *bazelPrebuiltEtc) Name() string {
-	return m.BaseModuleName()
-}
-
-func (m *bazelPrebuiltEtc) GenerateAndroidBuildActions(ctx android.ModuleContext) {}