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:

• Accepted the DCO. Commits without the DCO will delay acceptance.
• 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]

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 ⚠️

Additional details and impacted files

@@            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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