Coverage: add mapping file parsing in the reporter

This is in preparation of using the mapping file produced by Jack to
ignore shrunk classes/methods and restore the original names of
obfuscated classes/methods.

Adds unit tests to ensure we correctly parse the mapping file.

Bug: 31983791
Change-Id: Iac41c017128ad1c9c80ece9c2f1197bd35d7f1c8
4 files changed