Use more consistent *GetDatum() macros for some unsigned numbers

Use more consistent *GetDatum() macros for some unsigned numbers

This patch switches some code paths to use GetDatum() macros more in
line with the data types of the variables they manipulate.  This set of
changes does not fix a problem, but it is always nice to be more
consistent across the board.

Author: Kirill Reshke <reshkekirill@gmail.com>
Reviewed-by: Roman Khapov <rkhapov@yandex-team.ru>
Reviewed-by: Yuan Li <carol.li2025@outlook.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Man Zeng <zengman@halodbtech.com>
Discussion: https://postgr.es/m/CALdSSPidtC7j3MwhkqRj0K2hyp36ztnnjSt6qzGxQtiePR1dzw@mail.gmail.com