Reliable way to determine final analysis of a module

[MikhailArkhipov]

Continuation of #1143.

This will

• improve performance since we can delay some activities, such as linting run until everything is settled for the module.
• Prevent unnecessary reloads and reparses when AST was dropped too early per Drop AST for libraries after final analysis #1134 for Remove references to AST from analysis #1088 .
• Better determine when module analysis can be persisted into a database.

One possible way is to simulate analysis run, i.e.

Run all sessions but with only parsing in order determine final session and then
Run analysis without parsing repeating the above.
Technically end point should be the same.