sql: use row-level TTL for rangelog, eventlog and web_sessions

[aadityasondhi]

The system.web_session table is periodically purged. This is handled in purge_auth_seession.go and is controlled using cluster settings. An alternative (possibly better) would be to have the table configured with row-level ttl and have that manage these web_sessions.

Things to consider

• handling deleteOldExpiredSessionsStmt vs deleteOldRevokedSessionsStmt vs deleteSessionsAutoLogoutStmt
• we want the TTL to be configurable by the user, without a schema change on the table. This means possibly that the TTL expression should be able to refer to a cluster setting.

related: https://github.com/cockroachdb/cockroach/pull/88766

Jira issue: CRDB-20259

Epic CRDB-21265

[rafiss]

It would probably benefit from doing a bit of up-front investigation, since there might be some complexity with getting the jobs framework to operate on a system table.