Fix ABC alias for Python 3.10

[rtburns-jpl]

Aliases in collections.* to collections.abc.* have been removed starting
with python 3.10, so we must use the fully qualified import here.

I think this is needed since python/cpython#23754

[vjpbd]

I got the following error when first running ISCE after installing it with Python 3.10

File "/home/vjpbd/software/isce/v2.6.0/isce/components/iscesys/Component/TraitSeq.py", line 33, in <module>
    from collections import MutableSequence
ImportError: cannot import name 'MutableSequence' from 'collections' (/usr/lib/python3.10/collections/__init__.py)

I just change the aforementioned line to
from collections.abc import MutableSequence
and now it works fine.

Is it possible to add this fix to code?