44489: sql: bugfixes around writing the old primary key in pk changes r=rohany a=rohany

This PR fixes two bugs:
* The logic for when to rewrite the old primary key was broken
  resulting in the old primary key not being rewritten in many cases.
* The old primary key being created was not properly dealing with
  its dangling interleave information.

This PR makes the design decision to not re-interleave the copy of the old primary index if it was interleaved.

Release note: None

44551: jobs: always set start time of a job r=spaskob a=spaskob

When starting a job via CreateAndStartJob if
making the job started fails the job will stil be
in system.jobs and can be adopted by another
node later but the started time will be 0 in this
case. We add a check and set it if necessary.

Release note: none.

44553: engine: redefine targetSize and add maxSize to ExportToSst r=itsbilal a=ajwerner

This PR is a follow-up of work from #44440 motivated by problems unearthed while typing #44482. The PR comes in two commits:

1) Re-define `targetSize` from being a target below which most requests would remain to being the size above which the export stops.
2) Add a `maxSize` parameter above which the `ExportToSst` call will fail.

See the individual commits for more details. 

Co-authored-by: Rohan Yadav <rohany@alumni.cmu.edu>
Co-authored-by: Spas Bojanov <spas@cockroachlabs.com>
Co-authored-by: Andrew Werner <ajwerner@cockroachlabs.com>