backup: make LogBackupTemplate optional

[Ehco1996]

What problem does this PR solve?

ref #4955

What is changed and how does it work?

as title, this already fixed in #5137 for master, so we just need fix this for release-1.4 branch

Code changes

make BackupScheduleSpec.LogBackupTemplate optional on release-1.4

• 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.

none

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[codecov-commenter]

Codecov Report

Merging #5190 (17789bb) into release-1.4 (d3eb028) will decrease coverage by 0.02%.
The diff coverage is n/a.

Additional details and impacted files

@@               Coverage Diff               @@
##           release-1.4    #5190      +/-   ##
===============================================
- Coverage        58.90%   58.88%   -0.02%     
===============================================
  Files              227      227              
  Lines            26268    26268              
===============================================
- Hits             15473    15469       -4     
- Misses            9308     9311       +3     
- Partials          1487     1488       +1     

Flag	Coverage Δ
unittest	58.88% <ø> (-0.02%)	⬇️

[csuzhangxc]

/cherry-pick release-1.4

[ti-chi-bot]

@csuzhangxc: base branch (release-1.4) needs to differ from target branch (release-1.4).

In response to this:

/cherry-pick release-1.4

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[ti-chi-bot]

@csuzhangxc: The label(s) /release-1.4 cannot be applied, because the repository doesn't have them.

In response to this:

/cherry-pick release-1.4

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.