Add udtf SQL prefix

[SanjulaGanepola]

Changes

This PR adds udtf as a new SQL prefix for generating the skeleton for a user-defined table function as requested in #458

[github-actions]

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[forstie]

I think we should add some of the most important UDTF keywords.

NOT DETERMINISTIC
NO EXTERNAL ACTION
READS SQL DATA
SET OPTION
COMMIT = *NONE ,
DYNUSRPRF = *USER ,
USRPRF = *USER

[SanjulaGanepola]

I think we should add some of the most important UDTF keywords.

Done! I updated the screen cap above

[forstie]

ON Common1, I did
udtf: select * from dogshow.account

Any and all columns returned by the udtf should be referenced by name.
Using SELECT * means that the UDTF will break when a column is added later.

`-- statement:
-- select * from dogshow.account

-- User-defined table function
CREATE OR REPLACE FUNCTION MyFunction()
RETURNS TABLE (
CLINAME VARCHAR(100)
)
NOT DETERMINISTIC
NO EXTERNAL ACTION
READS SQL DATA
SET OPTION COMMIT = *NONE,
DYNUSRPRF = *USER,
USRPRF = *USER
BEGIN
RETURN select * from dogshow.account;
END;`

[forstie]

Delimited column names aren't handled by the support.
Example:

-- statement:
-- update: SELECT "cLo" FROM "CaMel"."CoWt"

-- User-defined table function
CREATE OR REPLACE FUNCTION MyFunction()
  RETURNS TABLE (
    cLo INTEGER
  )
  NOT DETERMINISTIC
  NO EXTERNAL ACTION
  READS SQL DATA
  SET OPTION COMMIT = *NONE,
             DYNUSRPRF = *USER,
             USRPRF = *USER
  BEGIN
    RETURN SELECT * FROM "CaMel"."CoWt";
  END;

[chrjorgensen]

@SanjulaGanepola See comments by @forstie for required changes.