pgsql: Allow using syncfs() in frontend utilities.

Allow using syncfs() in frontend utilities.

This commit allows specifying a --sync-method in several frontend
utilities that must synchronize many files to disk (initdb,
pg_basebackup, pg_checksums, pg_dump, pg_rewind, and pg_upgrade).
On Linux, users can specify "syncfs" to synchronize the relevant
file systems instead of calling fsync() for every single file.  In
many cases, using syncfs() is much faster.

As with recovery_init_sync_method, this new option comes with some
caveats.  The descriptions of these caveats have been moved to a
new appendix section in the documentation.

Co-authored-by: Justin Pryzby
Reviewed-by: Michael Paquier, Thomas Munro, Robert Haas, Justin Pryzby
Discussion: https://postgr.es/m/20210930004340.GM831%40telsasoft.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/8c16ad3b43299695f203f9157a2b27c22b9ed634

Modified Files
--------------
doc/src/sgml/config.sgml              | 12 +++---------
doc/src/sgml/filelist.sgml            |  1 +
doc/src/sgml/postgres.sgml            |  1 +
doc/src/sgml/ref/initdb.sgml          | 22 +++++++++++++++++++++
doc/src/sgml/ref/pg_basebackup.sgml   | 25 ++++++++++++++++++++++++
doc/src/sgml/ref/pg_checksums.sgml    | 22 +++++++++++++++++++++
doc/src/sgml/ref/pg_dump.sgml         | 21 ++++++++++++++++++++
doc/src/sgml/ref/pg_rewind.sgml       | 22 +++++++++++++++++++++
doc/src/sgml/ref/pgupgrade.sgml       | 23 ++++++++++++++++++++++
doc/src/sgml/syncfs.sgml              | 36 +++++++++++++++++++++++++++++++++++
src/bin/initdb/initdb.c               |  6 ++++++
src/bin/initdb/t/001_initdb.pl        | 12 ++++++++++++
src/bin/pg_basebackup/pg_basebackup.c |  7 +++++++
src/bin/pg_checksums/pg_checksums.c   |  6 ++++++
src/bin/pg_dump/pg_dump.c             |  7 +++++++
src/bin/pg_rewind/pg_rewind.c         |  8 ++++++++
src/bin/pg_upgrade/option.c           | 13 +++++++++++++
src/bin/pg_upgrade/pg_upgrade.c       |  6 ++++--
src/bin/pg_upgrade/pg_upgrade.h       |  1 +
src/fe_utils/option_utils.c           | 27 ++++++++++++++++++++++++++
src/include/fe_utils/option_utils.h   |  4 ++++
21 files changed, 271 insertions(+), 11 deletions(-)