pgsql: Remove MemoryContextContains().

Remove MemoryContextContains().

MemoryContextContains is no longer reliable in the wake of c6e0fe1f2,
because there's no longer very much redundancy in chunk headers.
(It wasn't *completely* reliable even before that, as there was a
chance of a false positive if you passed it something that didn't
point to an mcxt chunk at all.  But it was generally good enough.)

Hence, remove it.  There is no remaining core code that requires it.
Extensions that have been using it might be able to substitute a
test like "GetMemoryChunkContext(ptr) == context", recognizing that
this explicitly requires that the pointer point to some chunk.

Tom Lane and David Rowley

Discussion: https://postgr.es/m/1913788.1664898906@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/9543eff5e015b6f6f832da2d95d659629a2022f3

Modified Files
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src/backend/utils/mmgr/mcxt.c | 58 ++-----------------------------------------
src/include/utils/memutils.h  |  1 -
2 files changed, 2 insertions(+), 57 deletions(-)