Remember selection of dialog options for Python test generation

[tyuldashev]

Description
When user selects for example non default Test framework during test generation for Python then next time it's reset to default value. The same with other fields, with exception of 'Test source root'

To Reproduce

Steps to reproduce the behavior:

1. Open Python project
2. Invoke test generation dialog
3. Select Test framework = pytest
4. Generate tests
5. Invoke the dialog again

Expected behavior

pytest test framework is preserved

Actual behavior

test framework is Unittest again

Additional context

The same is with both timeouts and 'Visit only specified source'

[tyuldashev]

@tamarinvs19 please consult with @Vassiliy-Kudryashov about this one, this seems common problem with our dialogs and probably should be handled in some organized effort.

[tamarinvs19]

I found a problem with settings loading process from file: we cannot parse python test framework names (Unittest and pytest) from file and got error after IDE restarting.