mounter(ticdc): timezone fill default value should also consider tz.

[3AceShowHand]

What problem does this PR solve?

Issue Number: close #10931

What is changed and how it works?

• Ensure to correctly set the default value for the timestamp. It's in UTC and needs to be changed to the timezone set by TiCDC.

Check List

Tests

• Unit test
• Integration test

Questions

Will it cause performance regression or break compatibility?

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

Release note

`None`

[3AceShowHand]

/retest

[codecov]

Codecov Report

Merging #10932 (538fa51) into master (0ffc857) will increase coverage by 0.4151%.
Report is 7 commits behind head on master.
The diff coverage is 75.0000%.

Additional details and impacted files

Components	Coverage Δ
cdc	62.4612% <75.0000%> (+0.7359%)	⬆️
dm	51.2838% <ø> (+0.0424%)	⬆️
engine	63.4091% <ø> (ø)

Flag	Coverage Δ
unit	57.8327% <75.0000%> (+0.4151%)	⬆️

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

@@               Coverage Diff                @@
##             master     #10932        +/-   ##
================================================
+ Coverage   57.4176%   57.8327%   +0.4151%     
================================================
  Files           850        854         +4     
  Lines        125141     126347      +1206     
================================================
+ Hits          71853      73070      +1217     
+ Misses        47891      47881        -10     
+ Partials       5397       5396         -1     

[3AceShowHand]

/retest

[3AceShowHand]

/retest

[hongyunyan]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: asddongmen, hongyunyan

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• OWNERS [asddongmen,hongyunyan]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-04-22 10:13:10.005121871 +0000 UTC m=+851409.116168336: ☑️ agreed by asddongmen.
• 2024-04-23 02:12:10.635589114 +0000 UTC m=+53487.375492027: ☑️ agreed by hongyunyan.

[3AceShowHand]

/retest

[CharlesCheung96]

Is there any change in compatibility? If there is any change, please explain it in the pr body and add the release-note.

[3AceShowHand]

/retest

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #10946.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #10947.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #10948.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.0: #10949.

[3AceShowHand]

/cherry-pick release-8.1

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.1: #10963.

[ti-chi-bot]

@3AceShowHand: new pull request could not be created: failed to create pull request against pingcap/tiflow#release-8.1 from head ti-chi-bot:cherry-pick-10932-to-release-8.1: status code 422 not one of [201], body: {"message":"Validation Failed","errors":[{"resource":"PullRequest","code":"custom","message":"A pull request already exists for ti-chi-bot:cherry-pick-10932-to-release-8.1."}],"documentation_url":"https://docs.github.com/rest/pulls/pulls#create-a-pull-request"}

In response to this:

/cherry-pick release-8.1

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