tests: fix unstable integration_test gc_safepoint (#2717)

[ti-chi-bot]

This is an automated cherry-pick of #2717

What problem does this PR solve?

close #2653

What is changed and how it works?

record start_safepoint before check_safepoint_forward

Check List

Tests

• Integration test

Code changes

• Has exported function/method change

Side effects

None

Related changes

None

Release note

None

[ti-chi-bot]

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[amyangfei]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: cdef8e1

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (release-5.0@f264f84). Click here to learn what that means.
The diff coverage is n/a.

@@               Coverage Diff                @@
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  Hits                   ?      11053           
  Misses                 ?       7719           
  Partials               ?       1069           

[ti-chi-bot]

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