Python: Add type tracking for content

[RasmusWL]

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Attempts to add support for tracking more than just attribute content in type-trackers.

Adding the store/read steps is the most important part. This is PR is currently a draft, since there were some problems getting my tests to work (but this was fixed by https://github.com/github/codeql/pull/15755 and https://github.com/github/codeql/pull/15781)

Also, all the tests I wrote were against the call-graph. This was convenient since I knew them already, and I it's the motivation for adding this functionality... but thinking back it would have probably been more prudent to expand the core type-tracking tests instead.