pgsql: Implement List support for TransactionId

Implement List support for TransactionId

Use it for RelationSyncEntry->streamed_txns, which is currently using an
integer list.

The API support is not complete, not because it is hard to write but
because it's unclear that it's worth the code space, there being so
little use of XID lists.

Discussion: https://postgr.es/m/202205130830.g5ntonhztspb@alvherre.pgsql
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/f10a025cfe97c1a341f636368e67af5ca644c5d8

Modified Files
--------------
src/backend/nodes/list.c                    | 42 ++++++++++++++++++++++++++++-
src/backend/nodes/outfuncs.c                |  4 +++
src/backend/replication/pgoutput/pgoutput.c | 14 +++-------
src/include/nodes/nodes.h                   |  1 +
src/include/nodes/pg_list.h                 | 21 +++++++++++++++
5 files changed, 70 insertions(+), 12 deletions(-)