Use Soong modules for the NDK's extra STL libraries

* The extra STL libs are:

       libc++abi.a [needed for ndk_libc++_static]
       libandroid_support.a [always needed in NDK r16]
       libunwind.a [needed for ARM32]

 * The existing STL-dependency logic in linkShared only applies to shared
   libraries. By moving it to STL deps, the extra STL libs are linked into
   both shared libraries and executables.

 * Remove the ndk_prebuilt_library/ndkPrebuiltLibraryFactory module type,
   which is unused now.

 * Reuse the ndk_prebuilt_static_stl module type to describe the extra
   static libraries that are linked with both the static and shared libc++
   STLs.

Bug: b/73133405
Test: manual
Change-Id: I3f73e4f882d39e6efa470073bb4fc8c42dff8253

cc/library.go

@@ -601,25 +601,6 @@ func (library *libraryDecorator) linkShared(ctx ModuleContext,
 	sharedLibs := deps.SharedLibs
 	sharedLibs = append(sharedLibs, deps.LateSharedLibs...)
 
-	// TODO(danalbert): Clean this up when soong supports prebuilts.
-	if strings.HasPrefix(ctx.selectedStl(), "ndk_libc++") {
-		libDir := getNdkStlLibDir(ctx, "libc++")
-
-		if strings.HasSuffix(ctx.selectedStl(), "_shared") {
-			deps.StaticLibs = append(deps.StaticLibs,
-				libDir.Join(ctx, "libandroid_support.a"))
-		} else {
-			deps.StaticLibs = append(deps.StaticLibs,
-				libDir.Join(ctx, "libc++abi.a"),
-				libDir.Join(ctx, "libandroid_support.a"))
-		}
-
-		if ctx.Arch().ArchType == android.Arm {
-			deps.StaticLibs = append(deps.StaticLibs,
-				libDir.Join(ctx, "libunwind.a"))
-		}
-	}
-
 	linkerDeps = append(linkerDeps, deps.SharedLibsDeps...)
 	linkerDeps = append(linkerDeps, deps.LateSharedLibsDeps...)
 	linkerDeps = append(linkerDeps, objs.tidyFiles...)