IssueTracker

Since staleness will be a bigger problem with dex layout optimizations, we should have the baseline profile generation tasks report how stale your periodic / manual generation of profiles into the source directory is.

This will also help people determine how frequently to run the task.

E.g.:

> ./gradlew generateProfilesCommandToSrcDir
Updated baseline profiles in app/src/main
General
  1083 New rules            (2.5%)
  829  Removed rules        (1.9%)
Startup
  103 New startup rules     (6.5%)
  29  Removed startup rules (1.2%)

Consider https://github.com/JakeWharton/diffuse for inspiration here.