metrics/grafana: revert pr/30311 and fix the 'PD Client CMD Duration' panel (#46754)

[ti-chi-bot]

This is an automated cherry-pick of #46754

What problem does this PR solve?

Issue Number: close #30307

Problem Summary:

What is changed and how it works?

Something is wrong, I think I made some mistakes
This time it should be correct.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

tiup playground
explore & edit & export ...
import again & verify the changes ...

• 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

[ti-chi-bot]

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Adding the do-not-merge/cherry-pick-not-approved label.

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[ti-chi-bot]

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