sql: add parsing for LISTEN and NOTIFY statements

[asg0451]

Part of: #41522

Release note: None

[blathers-crl]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

It looks like your PR touches SQL parser code but doesn't add or edit parser tests. Please make sure you add or edit parser tests if you edit the parser.

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[cockroach-teamcity]

This change is