sql: support vector index creation

[DrewKimball]

This issue tracks adding support for vector index creation. We should support the following syntax:

CREATE VECTOR INDEX ...;
CREATE TABLE foo (..., VECTOR INDEX ...);
CREATE INDEX ... USING CSPANN;

support for this feature should include parsing, validating, and creating the index descriptor. We may also need to set up workers to maintain the index in the background.

Jira issue: CRDB-45998

Epic CRDB-49712

[DrewKimball]

Fixed by #140090 and #140437.