pgsql: Convert many uses of ReadBuffer[Extended](P_NEW) to ExtendBuffer

Convert many uses of ReadBuffer[Extended](P_NEW) to ExtendBufferedRel()

A few places are not converted. Some because they are tackled in later
commits (e.g. hio.c, xlogutils.c), some because they are more
complicated (e.g. brin_pageops.c). Having a few users of ReadBuffer(P_NEW) is
good anyway, to ensure the backward compat path stays working.

Discussion: https://postgr.es/m/20221029025420.eplyow6k7tgu6he3@awork3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/acab1b0914e426d28789731f50f5964dd4d2f054

Modified Files
--------------
contrib/bloom/blutils.c | 12 ++----------
src/backend/access/brin/brin.c | 9 ++++-----
src/backend/access/brin/brin_pageops.c | 4 ++++
src/backend/access/brin/brin_revmap.c | 15 +++------------
src/backend/access/gin/gininsert.c | 10 ++++------
src/backend/access/gin/ginutil.c | 12 ++----------
src/backend/access/gist/gist.c | 4 ++--
src/backend/access/gist/gistutil.c | 13 ++-----------
src/backend/access/hash/hashpage.c | 6 +++---
src/backend/access/nbtree/nbtpage.c | 34 +++++++++-------------------------
src/backend/access/nbtree/nbtree.c | 3 +++
src/backend/access/spgist/spgutils.c | 13 ++-----------
src/backend/commands/sequence.c | 3 ++-
13 files changed, 42 insertions(+), 96 deletions(-)