pgsql: pg_upgrade: Allow use of file cloning

pg_upgrade: Allow use of file cloning

Add another transfer mode --clone to pg_upgrade (besides the existing
--link and the default copy), using special file cloning calls.  This
makes the file transfer faster and more space efficient, achieving
speed similar to --link mode without the associated drawbacks.

On Linux, file cloning is supported on Btrfs and XFS (if formatted with
reflink support).  On macOS, file cloning is supported on APFS.

Reviewed-by: Michael Paquier <michael@paquier.xyz>

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3a769d8239afdc003c91a56d2d8d5adfadacda5d

Modified Files
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configure                        |  2 +-
configure.in                     |  1 +
doc/src/sgml/ref/pgupgrade.sgml  | 40 +++++++++++++++---
src/bin/pg_upgrade/check.c       | 13 +++++-
src/bin/pg_upgrade/file.c        | 90 ++++++++++++++++++++++++++++++++++++++++
src/bin/pg_upgrade/option.c      |  7 ++++
src/bin/pg_upgrade/pg_upgrade.h  |  6 ++-
src/bin/pg_upgrade/relfilenode.c | 44 +++++++++++++-------
src/include/pg_config.h.in       |  3 ++
9 files changed, 181 insertions(+), 25 deletions(-)