Implement tools to manage backup files

Summary:
This differential introduces API that allows to get the path to a backup file associated with particular backup ID and to remove backup files directory at once during
log-out.

Test Plan:

1. Call PlatformSpecificTools::getBackupFilePath() in C++ code which execution can be easily triggered manually (e.x. draft update).
2. Trigger execution of the code above.
3. Download application container from XCode or examine Device File Explorer in Android studio to ensure that empty backup directory was created.
4. Log out.
5. Examine application file system again. Ensure directory was deleted.

Reviewers: kamil, michal, bartek

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D10502