sql: support ordering by JSON (pq: unable to encode table key: *tree.DJSON)

Currently it's not possible to order a table by a JSON column or create a primary index on a JSON column.

This is because JSON does not have a valid lexicographic ordering.
This is incidentally the issue underlying #24436 and #35260.

for reference, PostgreSQL supports it.

See also #35730

Epic: CRDB-24501
Jira issue: CRDB-4564