sessiontxn/staleread: more accurate stale ts (#44272)

[ti-chi-bot]

This is an automated cherry-pick of #44272

What problem does this PR solve?

Issue Number: close #44215

Problem Summary:

What is changed and how it works?

When calculate as-of expr, calculate now expression by cached PD ts, the stale read ts will be more accurate, and there will also be less stale read fallback.

Check List

Tests

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

I also test with 100ms staleness read:

• resolved-ts.advance-ts-interval: 100ms

nightly:

this PR:

• resolved-ts.advance-ts-interval: 50ms

nightly:

this PR:

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.

Use more accurate stale read ts.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-7.1@25e2528). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.1     #45760   +/-   ##
================================================
  Coverage               ?   73.9828%           
================================================
  Files                  ?       1203           
  Lines                  ?     381299           
  Branches               ?          0           
================================================
  Hits                   ?     282096           
  Misses                 ?      81730           
  Partials               ?      17473           

[you06]

@cfzjywxk @zyguan PTAL

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cfzjywxk, crazycs520

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 [cfzjywxk,crazycs520]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-08-02 10:46:46.257381448 +0000 UTC m=+268690.199729977: ☑️ agreed by crazycs520.
• 2023-08-17 06:02:14.948343036 +0000 UTC m=+783699.497359023: ☑️ agreed by cfzjywxk.