Add SQLDialect.COCKROACHDB_23

[lukaseder]

The next version of COCKROACHDB 23 is already publishing beta releases:

• https://www.cockroachlabs.com/docs/releases/index.html#v23-1

New features that we can support, include:

• Support CockroachDB 23 user defined functions #13947
• Add native support for NULLS FIRST and NULLS LAST in CockroachDB 23 #15002 (actually a 22.1 feature, but it had many bugs)
• Add native support for CockroachDB 23 DELETE .. USING clause #15143
• Add runtime support for CockroachDB 23 UDTs #15145

Also, these improvements, which aren't strictly related to CRDB 23:

• Add native support for DELETE .. LIMIT and DELETE .. ORDER BY in CockroachDB #15144