Eliminate more detoast copies for packed varlenas

Ok, this removes what should be most if not all of the call sites where we're
detoasting text or byteas. In particular it gets all the regexp/like functions
and all the trim/pad functions. It also gets hashtext and hash_any.

$ zcat packed-varlena-efficiency_v0.patch.gz | diffstat
backend/access/hash/hashfunc.c | 12 !!
backend/utils/adt/like.c | 80 !!!!!!!!!!!!!!!!!!!
backend/utils/adt/oracle_compat.c | 157 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
backend/utils/adt/regexp.c | 119 !!!!!!!!!!!!!!!!!!!!!!!!!!!!
include/fmgr.h | 1
5 files changed, 5 insertions(+), 364 modifications(!)