Refactore context managers

[andreihrybo]

Implemented handling of revert_action in the context manager and added logging for the recover_notification message inside the context manager so that errors don’t need to be handled outside of it.
Updated/modified the logger methods so that it stores recover_notification separately for each context manager by pid. This will allow using a single logger for multiple context managers.
Wrote detailed tests for the context managers, simulating different points where errors can occur and how they are handled.
Updated the gcts branch update_filesystem method.

[jfilak]

I did review and created a new brach in this repo.

I squashed your commits (leaving out the cosmetic change):

• f730095

And then modified your changes to match my idea:

• e7b2815

[jfilak]

Thank you! I pushed 7d27fb9 to the branch master.