Add Windows IA2 support

[spectranaut]

This patch does the following:

1. Returns a serialized node for the MSAA/IA2 interface
2. Passes the test page title back with the ID. Otherwise, I was not able to find an easy way to poll the tree until the webpage is loaded. Sending the test page title will also allow us to know when it is time to poll again -- when a new test page has been loaded.

Requirements: comtypes python library

pip install comtypes

Running the code is the same as for other platforms:

# Chrome
python wpt run --force-renderer-accessibility --log-mach-level debug --log-mach - chrome core-aam/acacia/all_apis_example.html

# Firefox
python wpt run --no-headless --log-mach-level debug --log-mach - firefox core-aam/acacia/all_apis_example.html

The code to get access to IA2 interface was very inspired by James Teh's API test infrastructure in Firefox: https://searchfox.org/mozilla-central/source/accessible/tests/browser/windows/a11y_setup.py

[alice]

Lots of suggestions, but this is amazing.

[alice]

Suggested change

	if child.accName(CHILDID_SELF) == title:
	if child.accValue(CHILDID_SELF) == url:

(Not an actual suggestion to be applied directly, just documenting how we get the URL, if we wanted to do that)

[spectranaut]

done!

[alice]

If we sent location.href here instead of document.title, we could match based on the URL rather than the (potentially ambiguous) title.

[spectranaut]

good idea!