pgsql: Move routines to manipulate WAL into PostgreSQL::Test::Cluster

Move routines to manipulate WAL into PostgreSQL::Test::Cluster

These facilities were originally in the recovery TAP test
039_end_of_wal.pl. A follow-up bug fix with a TAP test doing similar
WAL manipulations requires them, and all these had better not be
duplicated due to their complexity. The routine names are tweaked to
use "wal" more consistently, similarly to the existing "advance_wal".

In v14 and v13, the new routines are moved to PostgresNode.pm.
039_end_of_wal.pl is updated to use the refactored routines, without
changing its coverage.

Reviewed-by: Alexander Kukushkin
Discussion: https://postgr.es/m/CAFh8B=mozC+e1wGJq0H=0O65goZju+6ab5AU7DEWCSUA2OtwDg@mail.gmail.com
Backpatch-through: 13

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/32a18cc0a73d8deb1e81d6ef8a9d5a6f300ed397

Modified Files
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src/test/perl/PostgreSQL/Test/Cluster.pm | 148 ++++++++++++++++++
src/test/recovery/t/039_end_of_wal.pl | 257 ++++++++-----------------------
2 files changed, 214 insertions(+), 191 deletions(-)