Modify namespace filter logic for backup with label selector

[blackpiglet]

Thank you for contributing to Velero!

Please add a summary of your change

• Add namespace tracker for backup item collector;
• Namespace tracker checks whether a namespace should be backed up according to the backup's namespace filter, backup label selector, and the backup or label selector;
• Namespace tracker will delete the namespaces not tracked from the backup;
• Add the size for the backup description output of the data-moved volumes.

Does your change fix a particular issue?

Fixes #7105

Please indicate you've done the following:

• [x] Accepted the DCO. Commits without the DCO will delay acceptance.
• [x] Created a changelog file or added /kind changelog-not-required as a comment on this pull request.
• [ ] Updated the corresponding documentation in site/content/docs/main.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 75.00000% with 44 lines in your changes are missing coverage. Please review.

Project coverage is 58.58%. Comparing base (f04fbbc) to head (884bcbe). Report is 6 commits behind head on main.

Files	Patch %	Lines
pkg/backup/item_collector.go	74.85%	36 Missing and 8 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #7697 +/- ## ========================================== + Coverage 58.49% 58.58% +0.08% ========================================== Files 343 343 Lines 28486 28592 +106 ========================================== + Hits 16664 16751 +87 - Misses 10406 10422 +16 - Partials 1416 1419 +3 ```

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