Add support for Postgres SIMILAR TO syntax

[andygrove]

Is your feature request related to a problem or challenge? Please describe what you are trying to do. Add support for Postgres SIMILAR TO syntax.

https://www.postgresql.org/docs/current/functions-matching.html#FUNCTIONS-SIMILARTO-REGEXP

Describe the solution you'd like Add support for Postgres SIMILAR TO syntax

Describe alternatives you've considered None

Additional context Depends on https://github.com/sqlparser-rs/sqlparser-rs/pull/569