grafana: add traffic metrics for staleread traffic

[you06]

What problem does this PR solve?

Issue Number: close #43325

Problem Summary:

What is changed and how it works?

With tikv/client-go#776, we can display the following metrics:

Before 15:15, the stale-read hit ratio is high, and after 15:15, there are over 80% stale-read misses. From the metrics, we can clearly find the traffic used by stale-read.

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.

Add traffic metrics for stale-read.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• cfzjywxk
• zyguan

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[cfzjywxk]

/merge

[ti-chi-bot]

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

Commit hash: ee32c5e

[you06]

/retest

[you06]

/cherry-pick release-6.5

[ti-chi-bot]

@you06: new pull request created to branch release-6.5: #44209.

In response to this:

/cherry-pick release-6.5

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[you06]

/cherry-pick release-7.1

[ti-chi-bot]

@you06: new pull request created to branch release-7.1: #44252.

In response to this:

/cherry-pick release-7.1

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.