Add support for reading DexGuard and ProGuard mapping files

[simonschiller]

What has changed

• We now read mapping files correctly for projects using DexGuard or ProGuard instead of R8.

Why was it changed

• Because not everybody is using R8 to obfuscate their projects.

Related issues

• See Incompatibility with DexGuard #87.

[MrHadiSatrio]

Huge thanks for this @simonschiller! I ran this change through DexGuard's sample project and I can see that class names are properly de-obfuscated. 🎉

However, a couple of points...

1. Unless DexGuard is configured with overwriteUnprotected == true, it will produce a separate AAB with -protected name suffix. In this case, variant.artifacts.get(SingleArtifact.BUNDLE) will not point to the correct artifact. I believe we should also handle this case within RulerPlugin.
2. Resource file names are still obfuscated and because of it attribution is currently broken.

MrHadiSatrio@67130e0 should address (1). I'd be elated if you can consider including it in this MR. 😃

[simonschiller]

Those two points are valid concerns and we should fix them, but I'll go ahead and merge this and we can open separate PRs to solve those issues (just to keep changes small and atomic)!