Fix incorrect uses of Datum conversion macros

Fix incorrect uses of Datum conversion macros

Since these macros just cast whatever you give them to the designated
output type, and many normal uses also cast the output type further, a
number of incorrect uses go undiscovered.  The fixes in this patch
have been discovered by changing these macros to inline functions,
which is the subject of a future patch.

Reviewed-by: Aleksander Alekseev <aleksander@timescale.com>
Discussion: https://www.postgresql.org/message-id/flat/8528fb7e-0aa2-6b54-85fb-0c0886dbd6ed%40enterprisedb.com