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>

Updated Authors from bk prs info

New directory structure:
- simulator source now in 'src' subdirectory
- imported files from 'ext' repository
- support building in arbitrary places, including
outside of the source tree. See comment at top
of SConstruct file for more details.
Regression tests are temporarily disabled; that
syetem needs more extensive revisions.

SConstruct:
Update for new directory structure.
Modify to support build trees that are not subdirectories
of the source tree. See comment at top of file for
more details.
Regression tests are temporarily disabled.
src/arch/SConscript:
src/arch/isa_parser.py:
src/python/SConscript:
Update for new directory structure.