Rethrow CancellationException to ensure stop by timeout

[dtim]

Description

Add CancellationException as the special case in the catch-all logging exception handler in TestCaseGenerator to ensure
that it is correctly propagated.

Fixes #1141

Type of Change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Automated Testing

No tests should break, no new automatic tests have been added.

Manual Scenario

Test generation for StringExamples should terminate in time.

Checklist (remove irrelevant options):

This is the author self-check list

• The change followed the style guidelines of the UTBot project
• Self-review of the code is passed
• The change contains enough commentaries, particularly in hard-to-understand areas
• New documentation is provided or existed one is altered
• No new warnings
• New tests have been added
• All tests pass locally with my changes