Leverage sqlparser-rs for query parsing.

[EvanHStanton]

cargo add sqlparser to introduce improved check and error response for validity of query input.

Example using invalid query "test":

pg_later=# select pglater.exec('select * from pg_available_extensions order by name limit 2') as job_id;
 
job_id
--------
      1
(1 row)

pg_later=# select pglater.exec('test') as job_id;
ERROR:  Query parsing failed, please submit a valid query: ParserError("Expected an SQL statement, found: test at Line: 1, Column 1")

[ChuckHend]

Add a test either in same file or in the integration tests then this is gtg!

[ChuckHend]

closes #46