*: Fix incorrect mapped allocation per thread metric (#18126)

[ti-chi-bot]

This is an automated cherry-pick of #18126

What is changed and how it works?

Issue Number: Close #18125

What's Changed:

Fix incorrect mapped allocation per thread metric

Not all thread builders are hooked by `thread_allocate_exclusive_arena`, so some threads are using shared arena, causing incorrect per thread allocation. 

Related changes

• [ ] PR to update pingcap/docs/pingcap/docs-cn:
• [x] Need to cherry-pick to the release branch

Check List

Tests

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

Side effects

• [ ] Performance regression: Consumes more CPU
• [ ] Performance regression: Consumes more Memory
• [ ] Breaking backward compatibility

Release note

Fix incorrect mapped allocation per thread metric

[ti-chi-bot]

@hhwyt This PR has conflicts, I have hold it. Please resolve them or ask others to resolve them, then comment /unhold to remove the hold label.

[hhwyt]

Here is the test result: https://github.com/tikv/tikv/pull/18563#issuecomment-2986482877.

[hhwyt]

Once #18563 is merged, I'll rebase the first commit from master.

[zhangjinpeng87]

bugbot run

[hhwyt]

@zhangjinpeng87

Bug: Metric Descriptor Missing in Collector

This is true but this does not affect Grafana Dashboard display, so can be ignored.

Bug: Thread Panic on Jemalloc Failure

This is true. While the error-handling can be more graceful as the arena allocation failure is a non-core logic should not cause TiKV panic, such failures are rare in practice, so I think it's ok to keep current implementation.

[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

• 2025-06-19 08:21:08.152141632 +0000 UTC m=+346320.875320614: :ballot_box_with_check: agreed by Connor1996.
• 2025-07-10 02:41:05.028607477 +0000 UTC m=+2140317.751786453: :ballot_box_with_check: agreed by LykxSassinator.

[hhwyt]

/hold

[glorv]

/retest

[hhwyt]

/hold

[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cfzjywxk, Connor1996, LykxSassinator

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• ~~OWNERS~~ [Connor1996,LykxSassinator,cfzjywxk]

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[hhwyt]

/unhold