Use source_module_name to determine the contents of prebuilt apexes

There are a couple of instances in apex/ and java/ that rely on the naming
convention that the jars exported by prebuilt apexes follow the name of
the java_sdk_library_import, minus the prebuilt_ prefix. With muliple
module sdk prebuilts in trunk stable, this naming convention might not
be valid. Use `source_module_name` instead.

```
prebuilt_sscp_fragment {name: "", contents: ["service-foo.v2"]}
java_import {name: "service-foo.v2", source_module_name: "service-foo"},
```

We should use service-foo and not service-foo.v2 because
1. The prebuilt apex contains service-foo.dex
2. PRODUCT_*JARS will contain service-foo and not service-foo.v2

For clarity, this CL does not drop the current mechanism where prebuilt bcp
fragments create a dependency edge to prebuilt java or java_sdk_library
imports. There is still some discussion around whether we can remove
that completely (b/320711431). If we were to do that, then the
Android.bp files will become

```
prebuilt_sscp_fragment {name: "", contents: ["service-foo"]}
```

Bug: 322175508

Test: Added a unit test

Test: In internal, lunch cf_x86_64_only_phone-next-userdebug && m
nothing # .ninja files identical

Test: In internal, created a parallel set of v2 prebuilts of
java_sdk_library_import and prebuilt_bcp_fragments for adservices && m
nothing # build passes

Change-Id: Ia899d75e826fa1a559368d706eaa65835f748d40

3 files changed, 10 insertions, 4 deletions

diff --git a/apex/prebuilt.go b/apex/prebuilt.go
index 399d9b92f..cebbae9a6 100644
--- a/apex/prebuilt.go
+++ b/apex/prebuilt.go
@@ -639,7 +639,7 @@ func (p *prebuiltCommon) createDeapexerModuleIfNeeded(ctx android.TopDownMutator
 			return false
 		}
 
-		name := android.RemoveOptionalPrebuiltPrefix(ctx.OtherModuleName(child))
+		name := java.ModuleStemForDeapexing(child)
 		if _, ok := tag.(android.RequiresFilesFromPrebuiltApexTag); ok {
 			commonModules = append(commonModules, name)
 
diff --git a/java/classpath_fragment.go b/java/classpath_fragment.go
index 201780175..0ebab4d8c 100644
--- a/java/classpath_fragment.go
+++ b/java/classpath_fragment.go
@@ -103,8 +103,8 @@ type classpathJar struct {
 func gatherPossibleApexModuleNamesAndStems(ctx android.ModuleContext, contents []string, tag blueprint.DependencyTag) []string {
 	set := map[string]struct{}{}
 	for _, name := range contents {
-		dep := ctx.GetDirectDepWithTag(name, tag)
-		set[name] = struct{}{}
+		dep, _ := ctx.GetDirectDepWithTag(name, tag).(android.Module)
+		set[ModuleStemForDeapexing(dep)] = struct{}{}
 		if m, ok := dep.(ModuleWithStem); ok {
 			set[m.Stem()] = struct{}{}
 		} else {
diff --git a/java/dexpreopt_bootjars.go b/java/dexpreopt_bootjars.go
index 01f60d403..f7e3cb93a 100644
--- a/java/dexpreopt_bootjars.go
+++ b/java/dexpreopt_bootjars.go
@@ -726,13 +726,19 @@ func (m *apexNameToApexExportsInfoMap) javaLibraryDexPathOnHost(ctx android.Modu
 	return nil, false
 }
 
+// Returns the stem of an artifact inside a prebuilt apex
+func ModuleStemForDeapexing(m android.Module) string {
+	bmn, _ := m.(interface{ BaseModuleName() string })
+	return bmn.BaseModuleName()
+}
+
 // Returns the java libraries exported by the apex for hiddenapi and dexpreopt
 // This information can come from two mechanisms
 // 1. New: Direct deps to _selected_ apexes. The apexes return a ApexExportsInfo
 // 2. Legacy: An edge to java_library or java_import (java_sdk_library) module. For prebuilt apexes, this serves as a hook and is populated by deapexers of prebuilt apxes
 // TODO: b/308174306 - Once all mainline modules have been flagged, drop (2)
 func getDexJarForApex(ctx android.ModuleContext, pair apexJarModulePair, apexNameToApexExportsInfoMap apexNameToApexExportsInfoMap) android.Path {
-	if dex, found := apexNameToApexExportsInfoMap.javaLibraryDexPathOnHost(ctx, pair.apex, android.RemoveOptionalPrebuiltPrefix(pair.jarModule.Name())); found {
+	if dex, found := apexNameToApexExportsInfoMap.javaLibraryDexPathOnHost(ctx, pair.apex, ModuleStemForDeapexing(pair.jarModule)); found {
 		return dex
 	}
 	// TODO: b/308174306 - Remove the legacy mechanism