Set targetsdkversion to future level if TARGET_BUILD_APPS is not empty

manifest_fixer transforms an AndroidManifest.xml file for use in aapt2.
For TARGET_BUILD_APPS builds, set targetSdkVersion to a FutureApiLevel

Test: In build/soong, go test ./java
Test: TH

Test: In internal, TARGET_BUILD_APPS=xyz m
out/soong/.intermediates/packages/providers/MediaProvider/MediaProvider/android_common_MediaProviderGoogle_apex30/package-res.apk
&& aapt2 dump badging
out/soong/.intermediates/packages/providers/MediaProvider/MediaProvider/android_common_MediaProviderGoogle_apex30/package-res.apk
| grep targetSdkVersion # targetSdkVersion:'10000'

Test: In internal, m
out/soong/.intermediates/packages/providers/MediaProvider/MediaProvider/android_common_MediaProviderGoogle_apex30/package-res.apk
&& aapt2 dump badging
out/soong/.intermediates/packages/providers/MediaProvider/MediaProvider/android_common_MediaProviderGoogle_apex30/package-res.apk
| grep targetSdkVersion # targetSdkVersion:'Tiramisu'

Bug: 204107787

Change-Id: Ic6f21111d5a8c61ae789a7a3a001f669257a39b2