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(-)