feat: support per-fragment vnode count #18444

3 / 4 tasks completed

1 task still to be completed

Task	Status
I have written necessary rustdoc comments	Completed
I have added necessary unit tests and integration tests	Completed
All checks passed in `./risedev check` (or alias, `./risedev c`)	Completed
My PR needs documentation updates. (Please use the Release note section below to summarize the impact on users)	Incomplete
#18515	Incomplete
#18529	Incomplete
#18444 👈	Incomplete
#18415	Incomplete
#18466	Incomplete
`main`	Incomplete