sql: add support for create/drop trigger

[DrewKimball]

This issue tracks adding support for creating and dropping a trigger on a table. This work will require updating function descriptors for trigger functions so that the function cannot be dropped and create a dangling reference. See the Postgres docs here: https://www.postgresql.org/docs/16/sql-createtrigger.html and here: https://www.postgresql.org/docs/16/sql-droptrigger.html

Epic CRDB-347

Jira issue: CRDB-39859