pgsql: Add test for pg_upgrade file transfer modes.

Add test for pg_upgrade file transfer modes.

This new test checks all of pg_upgrade's file transfer modes. For
each mode, we verify that pg_upgrade either succeeds (and some test
objects successfully reach the new version) or fails with an error
that indicates the mode is not supported on the current platform.
For cross-version tests, we also check that pg_upgrade transfers
non-default tablespaces. (Tablespaces can't be tested on same
version upgrades because of the version-specific subdirectory
conflict, but we might be able to enable such tests once we teach
pg_upgrade how to handle in-place tablespaces.)

Suggested-by: Robert Haas <robertmhaas(at)gmail(dot)com>
Reviewed-by: Andres Freund <andres(at)anarazel(dot)de>
Discussion: https://postgr.es/m/Zyvop-LxLXBLrZil%40nathan

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/af0d4901c1c39b3e3425522834708e0992592bb8

Modified Files
--------------
src/bin/pg_upgrade/meson.build | 1 +
src/bin/pg_upgrade/t/006_transfer_modes.pl | 101 +++++++++++++++++++++++++++++
src/test/perl/PostgreSQL/Test/Cluster.pm | 19 ++++++
src/test/perl/PostgreSQL/Test/Utils.pm | 25 +++++++
4 files changed, 146 insertions(+)