Bugfix | #2016 Fixed incorrect stubs generation for classes in the same namespace

[AlexNDRmac]

Hello!

• Type: bug fix
• Link to issue: Interface stubs have relative namespace #2016

In raising this pull request, I confirm the following:

• I have checked that another pull request for this purpose does not exist
• I wrote some tests for this PR
• I updated the CHANGELOG

Small description of change:

• fixed bug with stubs generation in case of relative namespaces for interfaces
• added test cases
• minor improvement for tests

Thanks

[codecov]

Codecov Report

Merging #2017 into development will increase coverage by <.01%.
The diff coverage is 100%.

@@                Coverage Diff                @@
##             development    #2017      +/-   ##
=================================================
+ Coverage          34.58%   34.58%   +<.01%     
- Complexity          8209     8210       +1     
=================================================
  Files                562      562              
  Lines              45300    45302       +2     
=================================================
+ Hits               15665    15667       +2     
  Misses             29635    29635

[sergeyklay]

Thank you!