pgsql: Remove dependency on HeapTuple from predicate locking functions.

Remove dependency on HeapTuple from predicate locking functions.

The following changes make the predicate locking functions more
generic and suitable for use by future access methods:

- PredicateLockTuple() is renamed to PredicateLockTID(). It takes
ItemPointer and inserting transaction ID instead of HeapTuple.

- CheckForSerializableConflictIn() takes blocknum instead of buffer.

- CheckForSerializableConflictOut() no longer takes HeapTuple or buffer.

Author: Ashwin Agrawal
Reviewed-by: Andres Freund, Kuntal Ghosh, Thomas Munro
Discussion: https://postgr.es/m/CALfoeiv0k3hkEb3Oqk%3DziWqtyk2Jys1UOK5hwRBNeANT_yX%2Bng%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/6f38d4dac381b5b8bead302a0b4f81761042cd25

Modified Files
--------------
src/backend/access/gin/ginbtree.c | 2 +-
src/backend/access/gin/ginfast.c | 2 +-
src/backend/access/gin/gininsert.c | 6 +-
src/backend/access/gist/gist.c | 2 +-
src/backend/access/hash/hashinsert.c | 2 +-
src/backend/access/heap/heapam.c | 125 ++++++++++++++++++++++++----
src/backend/access/heap/heapam_handler.c | 11 +--
src/backend/access/index/indexam.c | 4 +-
src/backend/access/nbtree/nbtinsert.c | 4 +-
src/backend/storage/lmgr/predicate.c | 137 ++++++++++---------------------
src/include/access/heapam.h | 2 +
src/include/storage/predicate.h | 9 +-
12 files changed, 176 insertions(+), 130 deletions(-)