Convert macros to static inline functions

Inspired by [0], I looked to convert more macros to inline functions.
The attached patches are organized "bottom up" in terms of their API
layering; some of the later ones depend on some of the earlier ones.

Note 1: Some macros that do by-value assignments like

#define PageXLogRecPtrSet(ptr, lsn) \
((ptr).xlogid = (uint32) ((lsn) >> 32), (ptr).xrecoff = (uint32) (lsn))

can't be converted to functions without changing the API, so I left
those alone for now.

Note 2: Many macros in htup_details.h operate both on HeapTupleHeader
and on MinimalTuple, so converting them to a function doesn't work in a
straightforward way. I have some in-progress work in that area, but I
have not included any of that here.

[0]:
https://www.postgresql.org/message-id/202203241021.uts52sczx3al@alvherre.pgsql