importer: Migrate to ElementTree API

[bearzly]

The ElementTree API is significantly faster than the minidom API, resulting in ~60% faster imports.

Major differences:

• Handling of XML namespaces (in minidom you would look for "spirit:name" but in ET you look for "{http://my/ns}name".
• ET does not provide a direct way to get the 'localName', so a helper was added to keep the code the same
• ET treats elements with no children as false-y, so some checks need to change to explicitly check for None

Besides those and some minor differences in the query API, this is essentialy a drop-in replacment.

[bearzly]

Benchmarked with python -m timeit -s 'from systemrdl import RDLCompiler; from peakrdl_ipxact import IPXACTImporter' 'rdlc = RDLCompiler(); ipxact = IPXACTImporter(rdlc); ipxact.import_file("some_ipxact.xml")'

Results from the 4 test XML files, as well as a vendor XML file that is 297 MB and has 73k registers

IP-XACT file	Before	After
generic_example_2009	20 loops, best of 5: 10.2 msec per loop	50 loops, best of 5: 4.44 msec per loop
generic_example_2014	20 loops, best of 5: 10.7 msec per loop	50 loops, best of 5: 4.6 msec per loop
nested_2009	5 loops, best of 5: 38.8 msec per loop	20 loops, best of 5: 16.8 msec per loop
nested_2014	5 loops, best of 5: 41.5 msec per loop	20 loops, best of 5: 17.5 msec per loop
giant	1 loop, best of 5: 114 sec per loop	1 loop, best of 5: 47.5 sec per loop

[bearzly]

Thanks for merging this so quickly! We work with a lot of massive IP-XACT files so I might come back with some more performance improvements in the future.

[amykyta3]

No problem! I'll hopefully deploy it within this coming week, but need to check compatibility against a few things first. A few tools I work with use this and extend/augment the behavior of the importer via vendor extensions.

[amykyta3]

Published in latest release. Thanks again!