Refactor PackageDexOptimizer

Split performDexoptLI in multiple smaller helpers. This will help in
adding the logic to process secondary dex files.

The goal is to move towards simple logic which can be reused between
compiling the package's code and its secondary dex files.

Test: device boots, packages get compiled in the background job,
      adb shell cmd package compile -m speed|speed-profile packageName

Bug: 32871170
Change-Id: I2d55edf42baa768f990939a82b3d52edf5f68a2c