[misc] Make check previous CI run only check for Build-and-Test jobs

[k-ye]

When the previous CI run's code format check fails, two thing happens:

1. @taichi-gardener will do a [skip ci] enforce code format to automatically correct the things
2. The second commit would still fail because it runs "Check the previous CI workflow" job, which finds that the previous workflow... has failed --> this time it fails again :-/

"Persubmit Checks / Code Format (pull_request)" is triggered unconditionally now, because it is a required check. (Previously it is disabled for @taichi-gardener 's commits)

Related issue = #1809

[Click here for the format server]

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[xumingkuan]

Cool, thanks!

[codecov]

Codecov Report

Merging #1899 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1899   +/-   ##
=======================================
  Coverage   43.81%   43.81%           
=======================================
  Files          45       45           
  Lines        6174     6174           
  Branches     1097     1097           
=======================================
  Hits         2705     2705           
  Misses       3300     3300           
  Partials      169      169           

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[k-ye]

Seems like we have one more thing to be addressed: "Build and Test (CPU) (ubuntu-latest, 3.6, OFF)" is a required check for merging, but it's skipped for @taichi-gardener 's commits. I probably need to add another job to gather the test result, and make that a required check instead...