pdClient (ticdc): Enable the pdClient forwarding function to make cdc more stable during network isolation between the PD leader (#11076)

[ti-chi-bot]

This is an automated cherry-pick of #11076

What problem does this PR solve?

Issue Number: close #10849

What is changed and how it works?

Enable pdClient's forwarding function, make it can forward request to PD follower if cdc is network isolated with PD Leader.

Enabling forwarding will introduce additional network round trips between the PD follower and PD leader. However, since TiCDC doesn't call the PD API frequently, it won't affect TiCDC's performance.

So we decide to enable it by default.

Check List

Tests

• Manual test (add detailed scripts or steps below)

This PR has been tested multiple times in the HA case [ha-ticdc-non-owner-random-to-pdleader-network-partition-last-for-10m]. The results indicate that it functions as expected:

The changefeed's lag is not affected by the network partition between CDC and the PD leader anymore.

Questions

Will it cause performance regression or break compatibility?

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

Release note

Enable the pdClient forwarding function to make cdc more stable during network isolation between the PD leader.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 9 lines in your changes are missing coverage. Please review.

❗ No coverage uploaded for pull request base (release-8.1@3a95436). Click here to learn what that means.

Additional details and impacted files

Components	Coverage Δ
cdc	61.7544% <0.0000%> (?)
dm	51.2608% <0.0000%> (?)
engine	63.4161% <0.0000%> (?)

Flag	Coverage Δ
unit	57.4588% <0.0000%> (?)

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

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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Needs approval from an approver in each of these files:

• OWNERS [asddongmen,sdojjy]
• cdc/api/v2/OWNERS [sdojjy]

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[asddongmen]

/retest