Fix: enable exclude filter for validation, rework partial update detection

[sale3]

Description (e.g. "Related to ...", etc.)

Reworks partial-update detection for exclude-filter flows. Updates with excluded targets are no longer treated as partial when all included repositories validate successfully, and last_validated_commit is now persisted for those runs.

Tested the following:

• Cloned with repo clone --exclude-filter "repo['type']=='html'" git@github.com:oll-test-repos/mohicanlaw-law.git

• Ran taf repo update and confirmed that the html repo was not cloned

• Deleted the exclude-filter entry from last_validated_commit and confirmed that the repo was cloned as expected

• Deleted last_validated_commit and ran update, condifrming that the validation started from the beginning and was completed successfully.

• Ran integration tests

• Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)

• Title summarizes what is changing

• Commit messages are meaningful (see this for details)

• Tests have been included and/or updated, as appropriate
  Docstrings have been included and/or updated, as appropriate

• Changelog has been updated, as needed (see CHANGELOG.md)

[CLAassistant]

All committers have signed the CLA.

[n-dusan]

question (non-blocking): is it worth adding tests for exclude-filter scenarios to reduce the need for manual testing, especially once codify rolls out?