Merge cockroachdb#38782

38782: storage: persist minimum transaction timestamps in intents r=nvanbenschoten a=nvanbenschoten

Fixes cockroachdb#36089.
Informs cockroachdb#37199.

This commit addresses the second concern from cockroachdb#37199 (comment) by implementing its suggestion #1.

It augments the TxnMeta struct to begin storing the transaction's minimum timestamp. This allows pushers to have perfect accuracy into whether an intent is part of a transaction that can eventually be committed or whether it has been aborted by any other pusher and uncommittable.

This allows us to get rid of the false positive cases where a pusher incorrectly detects that a transaction is still active and begins waiting on it. In this worst case, this could lead to transactions waiting for the entire transaction expiration for a contending txn.

@tbg I'm assigning you because you reviewed most of the lazy transaction record stuff (especially cockroachdb#33523), but let me know if you'd like me to find a different reviewer.

Co-authored-by: Nathan VanBenschoten <nvanbenschoten@gmail.com>