pgsql: Rename ShmemVariableCache to TransamVariables

Rename ShmemVariableCache to TransamVariables

The old name was misleading: It's not a cache, the values kept in the
struct are the authoritative source.

Reviewed-by: Tristan Partin, Richard Guo
Discussion: https://www.postgresql.org/message-id/6537d63d-4bb5-46f8-9b5d-73a8ba4720ab@iki.fi

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b31ba5310b5176402b60abc0454a033b1210ab75

Modified Files
--------------
contrib/amcheck/verify_heapam.c | 14 +--
src/backend/access/transam/clog.c | 6 +-
src/backend/access/transam/commit_ts.c | 44 +++++-----
src/backend/access/transam/subtrans.c | 4 +-
src/backend/access/transam/twophase.c | 12 +--
src/backend/access/transam/varsup.c | 104 +++++++++++------------
src/backend/access/transam/xlog.c | 54 ++++++------
src/backend/access/transam/xlogreader.c | 4 +-
src/backend/access/transam/xlogrecovery.c | 2 +-
src/backend/postmaster/autovacuum.c | 4 +-
src/backend/storage/ipc/procarray.c | 66 +++++++-------
src/backend/storage/lmgr/predicate.c | 2 +-
src/backend/utils/adt/xid8funcs.c | 10 +--
src/include/access/transam.h | 10 +--
src/include/storage/standby.h | 2 +-
src/include/storage/standbydefs.h | 2 +-
src/test/modules/xid_wraparound/xid_wraparound.c | 4 +-
src/tools/pgindent/typedefs.list | 3 +-
18 files changed, 172 insertions(+), 175 deletions(-)