Add '--ignore-errors' into pg_regress

Hi,

I want to add the '--ignore-errors' option into the pg_regress module.

I understand it can't be used in the regression or TAP tests. But such
option is useful to test a custom extension. A custom extension couldn't
pass all check-world tests and will be stopped at the end of first stage.
My use case of this feature is to run check-world, look for core files
and analyze diffs of failed (but ignored) tests. Maybe it is not
difficult to apply this patch before the test in CI script, but annoying
procedure.
I think this patch could be applied because it is trivial and can be
easy reverted if needed.

An example:
TEMP_CONFIG=/tmp/extra.config \
EXTRA_REGRESS_OPTS="--load-extension=aqo --ignore-errors
--schedule=src/test/regress/parallel_schedule" \
make check-world

Maybe I just don't know the right way?

--
regards,
Andrey Lepikhov
Postgres Professional