Integrate ClassLoaderContext check in OatFileAssistant::GetBestOatFile.

This reduces some code duplication between
OatFileManager::OpenDexFilesFromOat and GetDexoptNeeded.

It also gives the chance for OatFileAssistant and GetDexoptNeeded to
find the real best oat file.

Test: test.py
Bug: 176960283
Change-Id: Id366aef7a9e91833d8edaea965abda4cfdcd8455
8 files changed