kvserver: cpu based load splitting #95377
Description
In #90574 we added support for finding a split point of a range based on a weighted midpoint. Previously, only unweighted midpoints e.g. all queries=1 was supported.
This issue is to integrate this weighted split finder with request cpu and instrument cpu based load splitting.
additional considerations
The merge queue uses with the load of a range and the load split threshold when deciding whether to merge two adjacent ranges. These are collected via RPC. This presents an issue in
- mixed version
Additional fields may not be populated for CPU, so a fallback is needed.
- in-between or shortly after switching cpu/qps based load splitting
Similar issue to above.
Jira issue: CRDB-23491