scripts/get_abi.py: add support for undefined ABIs

scripts/get_abi.py: add support for undefined ABIs

The undefined logic is complex and has lots of magic on it.

Implement it, using the same algorithm we have at get_abi.pl. Yet,
some tweaks to optimize performance and to make the code simpler
were added here:
- at the perl version, the tree graph had loops, so we had to
  use BFS to traverse it. On this version, the graph is a tree,
  so, it simplifies the what group for sysfs aliases;
- the logic which splits regular expressions into subgroups
  was re-written to make it faster;
- it may optionally use multiple processes to search for symbol
  matches;
- it has some additional debug levels.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/1529c255845d117696d5af57d8dc05554663afdf.1739182025.git.mchehab+huawei@kernel.org