Add WAL write metric

[v01dstar]

cherry-pick of https://github.com/tikv/rocksdb/pull/153

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[APPROVALNOTIFIER] This PR is APPROVED

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

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/tikv/rocksdb/blob/8.10.tikv/OWNERS)~~ [Connor1996,LykxSassinator] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

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[LGTM Timeline notifier]

Timeline:

• 2024-09-27 03:15:58.647727271 +0000 UTC m=+1795028.388151195: :ballot_box_with_check: agreed by LykxSassinator.
• 2024-09-27 05:28:58.073923113 +0000 UTC m=+1803007.814347047: :ballot_box_with_check: agreed by Connor1996.