Improve memory after restart

[CalvinNeo]

What problem does this PR solve?

Issue Number: ref #7564

Problem Summary:

1. Reduce memory after restart
2. Improve metrics

What is changed and how it works?

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

None

[CalvinNeo]

/run-build-release comment=true

[sre-bot]

download tiflash binary(linux amd64) at http://fileserver.pingcap.net/download/builds/pingcap/test/tiflash/68cde7c192354417ccce1c6e8d03561e579d5dad/centos7/tiflash-linux-amd64.tar.gz

[CalvinNeo]

/run-build-release comment=true

[sre-bot]

download tiflash binary(linux amd64) at http://fileserver.pingcap.net/download/builds/pingcap/test/tiflash/330f07fe6680bfeb2f8a9a8b79edff6de011a08b/centos7/tiflash-linux-amd64.tar.gz

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JinheLin, Lloyd-Pottiger

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [JinheLin,Lloyd-Pottiger]

Approvers can indicate their approval by writing /approve in a comment
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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-08-21 02:23:47.928796928 +0000 UTC m=+1116192.477812914: ☑️ agreed by JinheLin.
• 2023-08-23 05:52:21.653760515 +0000 UTC m=+1301506.202776514: ☑️ agreed by Lloyd-Pottiger.