Add pg_dissect_walfile_name()

Add pg_dissect_walfile_name()

This function takes in input a WAL segment name and returns a tuple made
of the segment sequence number (dependent on the WAL segment size of the
cluster) and its timeline, as of a thin SQL wrapper around the existing
XLogFromFileName().

This function has multiple usages, like being able to compile a LSN from
a file name and an offset, or finding the timeline of a segment without
having to do to some maths based on the first eight characters of the
segment.

Bump catalog version.

Author: Bharath Rupireddy
Reviewed-by: Nathan Bossart, Kyotaro Horiguchi, Maxim Orlov, Michael
Paquier
Discussion: https://postgr.es/m/CALj2ACWV=FCddsxcGbVOA=cvPyMr75YCFbSQT6g4KDj=gcJK4g@mail.gmail.com