pgsql: Add pg_dump support for ALTER obj DEPENDS ON EXTENSION

Add pg_dump support for ALTER obj DEPENDS ON EXTENSION

pg_dump is oblivious to this kind of dependency, so they're lost on
dump/restores (and pg_upgrade). Have pg_dump emit ALTER lines so that
they're preserved. Add some pg_dump tests for the whole thing, also.

Reviewed-by: Tom Lane (offlist)
Reviewed-by: Ibrar Ahmed
Reviewed-by: Ahsan Hadi (who also reviewed commit 899a04f5ed61)
Discussion: https://postgr.es/m/20200217225333.GA30974@alvherre.pgsql

Branch
------
REL_12_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/f977e6dec8a01f32eee0ccfafc80646d3546b8f7

Modified Files
--------------
src/bin/pg_dump/common.c | 1 +
src/bin/pg_dump/pg_dump.c | 107 +++++++++++++++++++++++++---
src/bin/pg_dump/pg_dump.h | 1 +
src/test/modules/test_pg_dump/t/001_base.pl | 32 +++++++++
4 files changed, 133 insertions(+), 8 deletions(-)