pg_recvlogical: Rename --two-phase and --failover options.

pg_recvlogical: Rename --two-phase and --failover options.

This commit renames the pg_recvlogical options --two-phase and
--failover to --enable-two-phase and --enable-failover, respectively.
The new names distinguish these enabling options from action options
like --start and --create-slot, while clearly indicating their purpose
to enable specific logical slot features.

The option --failover is new in PostgreSQL 18 (commit cf2655a9029), so
no compatibility break there.  The option --two-phase has existed
since PostgreSQL 15 (commit cda03cfed6b), so for compatibility we keep
the old option name --two-phase around as deprecated.

Also note that pg_createsubscriber has acquired an --enable-two-phase
option, so this increases consistency across tools.

Co-authored-by: Masahiko Sawada <sawada.mshk@gmail.com>
Discussion: https://postgr.es/m/a28f66df-1354-4709-8d63-932ded4cac35@eisentraut.org