pgsql: Fixes for vacuum_cleanup_index_scale_factor GUC option

Fixes for vacuum_cleanup_index_scale_factor GUC option

vacuum_cleanup_index_scale_factor was located in autovacuum group of
GUCs.  However, it affects not only autovacuum, but also manually run
VACUUM.  It appears that "client connection defaults" group of GUCs
is more appropriate for vacuum_cleanup_index_scale_factor, because
vacuum_*_age options are already located there.

Also, vacuum_cleanup_index_scale_factor was missed in
postgresql.conf.sample.  So, add it there with appropriate comment.

Author: Masahiko Sawada with minor editorization by me
Discussion: https://postgr.es/m/CAD21AoArsoXMLKudXSKN679FRzs6oubEchM53bHwn8Tp%3D2boNg%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/9a994e37e08df3578f52011543dc28085dc18e21

Modified Files
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doc/src/sgml/config.sgml                      | 83 +++++++++++++--------------
src/backend/utils/misc/guc.c                  |  2 +-
src/backend/utils/misc/postgresql.conf.sample |  3 +
3 files changed, 43 insertions(+), 45 deletions(-)