sink/mysql(ticdc): rename syncpointStore.go to syncpoint_store.go

[Rustin170506]

What problem does this PR solve?

Issue Number: ref #5138

What is changed and how it works?

rename syncpointStore.go to syncpoint_store.go. It is not a standard naming.

Check List

Tests

• No code

Questions

Will it cause performance regression or break compatibility?

No

Do you need to update user documentation, design documentation or monitoring documentation?

No

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• CharlesCheung96

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[codecov-commenter]

Codecov Report

Merging #5506 (daf71d5) into master (e62fbea) will decrease coverage by 0.1736%.
The diff coverage is n/a.

Flag	Coverage Δ
cdc	61.4772% <ø> (-0.0093%)	⬇️
dm	51.9500% <ø> (-0.0164%)	⬇️
engine	?

Flags with carried forward coverage won't be shown. Click here to find out more.

@@               Coverage Diff                @@
##             master      #5506        +/-   ##
================================================
- Coverage   56.3160%   56.1423%   -0.1737%     
================================================
  Files           675        530       -145     
  Lines         78594      69965      -8629     
================================================
- Hits          44261      39280      -4981     
+ Misses        30143      26915      -3228     
+ Partials       4190       3770       -420     

[Rustin170506]

/merge

[ti-chi-bot]

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

Commit hash: daf71d5