br: add incremental backup size for volume snapshot backup (#5188)

[ti-chi-bot]

This is an automated cherry-pick of #5188

What problem does this PR solve?

Add incremental backup size for volume snapshot backup

Close #5187

What is changed and how does it work?

Code changes

• Has Go code change
• Has CI related scripts change

Tests

• Unit test
• E2E test
• Manual test
• No code

Side effects

• Breaking backward compatibility
• Other side effects:

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Release Notes

Please refer to Release Notes Language Style Guide before writing the release note.

[ti-chi-bot]

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[codecov-commenter]

Codecov Report

Merging #5211 (5e82676) into release-1.5 (7330207) will decrease coverage by 0.19%.
The diff coverage is 0.00%.

Additional details and impacted files

@@               Coverage Diff               @@
##           release-1.5    #5211      +/-   ##
===============================================
- Coverage        57.94%   57.76%   -0.19%     
===============================================
  Files              248      248              
  Lines            29343    29430      +87     
===============================================
- Hits             17003    17000       -3     
- Misses           10692    10779      +87     
- Partials          1648     1651       +3     

Flag	Coverage Δ
unittest	57.76% <0.00%> (-0.19%)	⬇️