Storages: Refine SegmentReadTaskScheduler::add to reduce lock contention (#9027)

[ti-chi-bot]

This is an automated cherry-pick of #9027

What problem does this PR solve?

Issue Number: close #9024

What is changed and how it works?

• Add pending_pools: pools from computational layer will be added to pending_pools and can return immediately.
• sched_thread will reap pending_pools before calling scheduleOneRound.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
  • Run queries without any exceptions.
• 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

[JinheLin]

/run-all-tests

[JinheLin]

/run-integration-test

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JaySon-Huang, JinheLin

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Needs approval from an approver in each of these files:

• OWNERS [JaySon-Huang,JinheLin]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-06-04 02:48:04.085055714 +0000 UTC m=+3349437.842191287: ☑️ agreed by JinheLin.
• 2024-06-04 05:09:34.444221761 +0000 UTC m=+3357928.201357315: ☑️ agreed by JaySon-Huang.