Use BaseModuleName() + SubName as apexFile.moduleName

This change fixes this error:
```
TARGET module com.android.adbd.flattened requires non-existent TARGET
module: prebuilt_libclang_rt.ubsan_standalone-arm-android
```

apexFile.moduleName is used as Make dependency name, so it should use
m.BaseModuleName() instead of m.Name(), because soong may prepend
"prebuilt_" to or mutate the output of m.Name() in other ways.

android/androidmk.go emits Android.mk modules with
`LOCAL_MODULE := module.BaseModuleName() + <SubName>`, so replace
apexFile.moduleName with BaseModuleName() + <SubName> as much as
possible.

Bug: 7456955
Test: Add unit test in apex/apex_test.go
Test: lunch blueline_hwasan && SANITIZE_TARGET='hwaddress fuzzer' m nothing
Test: Verify out/soong/Android-blueline_hwasan.mk
Change-Id: If8537fc1bedbe6c3405de3662a5df210a073c43f