lightning: always get latest PD leader when access PD after initialized (#46726)

[ti-chi-bot]

This is an automated cherry-pick of #46726

What problem does this PR solve?

Issue Number: close #46688 close #43436

Problem Summary:

What is changed and how it works?

PD nodes may change, so lightning should always try to use latest informtion rather than the addresses in task configuration.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[lance6716]

waiting for #45726

[D3Hunter]

/lgtm

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: D3Hunter, lance6716

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-10-17 02:43:29.39033071 +0000 UTC m=+1711406.977440854: ☑️ agreed by D3Hunter.
• 2023-10-17 02:53:34.0749094 +0000 UTC m=+1712011.662019544: ☑️ agreed by lance6716.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-7.1@acdac74). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

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