sql: rename setting disable_plan_gists to plan_gists_enabled

[rytaft]

This would be more consistent with all other setting names and avoid setting a bad precedent

Jira issue: CRDB-11552

[cucaroach]

Yeah I went back and forth on this and went with the default where the Go default value (false) gave us the behavior we wanted because of #70888. I think I was following the precedent of "disable_partially_distributed_plans"

[rytaft]

Seems like that might have been a mistake too -- most other boolean settings end with _enabled, and I think that matches up with what was discussed here: https://github.com/cockroachdb/cockroach/blob/master/docs/RFCS/20170317_settings_table.md#naming-the-last-part

[github-actions]

We have marked this issue as stale because it has been inactive for
18 months. If this issue is still relevant, removing the stale label
or adding a comment will keep it active. Otherwise, we'll close it in
10 days to keep the issue queue tidy. Thank you for your contribution
to CockroachDB!

[mgartner]

I think the ship has sailed on this one. Closing.