Cache management API

[tobrun]

Follow up from #14925

Checklist:

• integration
  • MVP
  • add javadoc
  • post callback to main thread
  • add instrumentation tests
  • check if filesource is not activated else call callback with error message
• test app example

[chloekraw]

from #14978:

Revise existing documentation to clarify that MGLOfflineStorage manages both offline packs - and the ambient cache

does this need to be done on Android too? our offline/caching setup can be a bit confusing; I'd like to make sure it's clearly documented and communicated to customers

[tobrun]

@chloekraw

Revise existing documentation to clarify that MGLOfflineStorage manages both offline packs - and the ambient cache

does this need to be done on Android too? our offline/caching setup can be a bit confusing; I'd like to make sure it's clearly documented and communicated to customers

I'm currently exposing this on the FileSource API and not the OfflineManger API on Android. (I don't believe that iOS supports the filesource concept). I could move it to the same component as iOS if we need to better align the APIs.

[tobrun]

This PR also needs to add integration of invalidateOfflineRegion

[chloekraw]

🎉 thanks for the quick work on this, @tobrun + @langsmith! Let's hold on merging until the iOS side is ready and we can do a final compare + FAQ review.

@langsmith: could you add details of how customers should use each of the APIs implemented here (with code snippets) and when they should use them into the FAQ?

[julianrex]

cc @jmkiley

[zugaldia]

Capturing chat with @chloekraw, we're good to move forward with this PR as well as continuing the reference implementation work on the Demo App.

[chloekraw]

Capturing chat with @chloekraw, we're good to move forward with this PR as well as continuing the reference implementation work on the Demo App.

yep! I just added two in-line documentation comments

[tobrun]

yep! I just added two in-line documentation comments

comments addressed, thank you for 👀'ing !