base,python: Fix to allow multiple --debug-ignore values.

base,python: Fix to allow multiple --debug-ignore values.

When adding multiple SimObjects to --debug-ignore, either separating the values with
a colon or adding multiple --debug-ignore flags, the previous code only ignored the
last SimObject in the list.  This changeset adds and uses new `ObjectMatch::add` and
`Logger::addIgnore` methods to make the functionality of the flag consistent with
its description.

Change-Id: Ib6967a48611ea59a211f81af2a970c4de429b1be
Signed-off-by: Isaac Sánchez Barrera <isaac.sanchez@bsc.es>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17488
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>