pgsql: Doc: various improvements for pg_basebackup reference page.

Doc: various improvements for pg_basebackup reference page.

Put the -r option in the right section (it certainly isn't an
option controlling "the location and format of the output").

Clarify the behavior of the tablespace and waldir options
(that part per gripe from robert(at)interactive(dot)co(dot)uk).

Make a large number of small copy-editing fixes in text that
visibly wasn't written by native speakers, and try to avoid
grammatical inconsistencies between the descriptions of
the different options.

Back-patch to v13, since HEAD hasn't meaningfully diverged yet.

Discussion: https://postgr.es/m/159749418850.14322.216503677134569752@wrigleys.postgresql.org

Branch
------
REL_13_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/277e49eca73a719695d0b74360b54124e76c6833

Modified Files
--------------
doc/src/sgml/ref/pg_basebackup.sgml | 330 +++++++++++++++++++-----------------
1 file changed, 174 insertions(+), 156 deletions(-)