admission: async compaction cause disk bandwidth spikes

[aadityasondhi]

We noticed in https://github.com/cockroachdb/cockroach/issues/131484#issuecomment-2397597539 that async compactions in pebble cause spikes in disk bandwidth, ultimately leading to the assertion failure since the disk bandwidth limiter cannot account for these reads and writes until after the 15s adjustment interval.

We can attribute these writes as error term in our write amp linear model and should account for them at a higher frequency. We discussed the implementation of such accounting internally.

Jira issue: CRDB-42982

Epic CRDB-37479

[blathers-crl[bot]]

Hi @aadityasondhi, please add branch-* labels to identify which branch(es) this C-bug affects.

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