Use mapping hash as input for generate uuid task

[romtsn]

📜 Description

• When isIncludeAndroidResources is enabled, it also runs android resources/assets generation tasks so they are available in robolectric tests. Since our generateUuid task was depending on the mapping file (use source files as input for generating uuids and source bundle #634), minifyReleaseWithR8 task was also triggered when running robolectric tests.
• Instead we now set file hash as task property:
  • This still ensures the task is only running when the mapping file contents changed
  • But this does not trigger the minify task for robolectric tests (which is what we want!)
  • Additional optimization is that we also read the top lines of the mapping file, which usually contains a SHA-256 hash generated by r8 itself, and use it. This helps us with big files especially, because we don't need to generate hash of their contents (which can take multiple seconds)

💡 Motivation and Context

Internal report from a customer

💚 How did you test it?

manually + automated

📝 Checklist

• I reviewed the submitted code
• I added tests to verify the changes
• I updated the docs if needed
• No breaking changes

🔮 Next steps

[adinauer]

LGTM