Extend `PostgresqlSqlLexer` to handle PG14 SQL-standard function body syntax

[mp911de]

PG14 added a new syntax for creating SQL functions that we should support with PostgresqlSqlLexer

CREATE OR REPLACE FUNCTION asterisks(n int)
  RETURNS SETOF text
  LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
BEGIN ATOMIC
SELECT repeat('*', g) FROM generate_series (1, n) g; -- <-- Note this semicolon
END;

Right now, PostgresqlSqlLexer.tokenize(…) identifies this above as two statements. See also:

• bug: Parser does not handle new version 14 function definition syntax pgjdbc#2506
• New PG14 SQL-standard function bodies break our SQL parser npgsql/npgsql#4445

[mp911de]

/cc @toverdijk

[toverdijk]

It does seem quite complex - I guess also the sql body needs to be parsed completely as well in order to catch commented out ENDs and such. I'll give it a shot..