pgsql: pg_upgrade: Parallelize incompatible polymorphics check.

pg_upgrade: Parallelize incompatible polymorphics check.

This commit makes use of the new task framework in pg_upgrade to
parallelize the check for usage of incompatible polymorphic
functions, i.e., those with arguments of type anyarray/anyelement
rather than the newer anycompatible variants. This step will now
process multiple databases concurrently when pg_upgrade's --jobs
option is provided a value greater than 1.

Reviewed-by: Daniel Gustafsson, Ilya Gladyshev
Discussion: https://postgr.es/m/20240516211638.GA1688936%40nathanxps13

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/cf2f82a37cc35895b67c83dd2b33d2fcf4688a55

Modified Files
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src/bin/pg_upgrade/check.c | 159 +++++++++++++++++++++++----------------------
1 file changed, 83 insertions(+), 76 deletions(-)