Add types for prosemirror.model

[sciyoshi]

I've been chipping away at this over the past few days. Most of the types came from using monkeytype, then some manual updates to change code to match upstream which wasn't caught with the switchover to TypeScript.

This also uncovered a few bugs that were not identified by tests:

• Invalid parameter passed here: https://github.com/fellowapp/prosemirror-py/compare/typing-2?expand=1#diff-bf164a257a2fcf347981ef1e822918dc6b1fcaaebedab25b62549f943d599ae9R286
• A few places where callbacks were being passed the wrong number of arguments, which is something that works fine in JS but breaks in Python unless you add *args.

After this it would be nice to add some types from prosemirror.transform, as well as switch a few things over to dataclasses, and maybe experiment with compilation with mypyc... 👀

[codecov]

Codecov Report

Attention: 83 lines in your changes are missing coverage. Please review.

Comparison is base (8b3c7e5) 82.63% compared to head (b061e0e) 83.07%.

Files	Patch %	Lines
prosemirror/model/content.py	87.95%	20 Missing ⚠️
prosemirror/transform/step.py	77.14%	8 Missing ⚠️
prosemirror/model/from_dom.py	66.66%	7 Missing ⚠️
prosemirror/model/node.py	91.86%	7 Missing ⚠️
prosemirror/transform/map.py	88.88%	6 Missing ⚠️
prosemirror/transform/mark_step.py	87.23%	6 Missing ⚠️
prosemirror/transform/transform.py	92.10%	6 Missing ⚠️
prosemirror/model/replace.py	91.11%	4 Missing ⚠️
prosemirror/model/schema.py	97.05%	4 Missing ⚠️
prosemirror/transform/structure.py	86.66%	4 Missing ⚠️
... and 7 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #233      +/-   ##
==========================================
+ Coverage   82.63%   83.07%   +0.44%     
==========================================
  Files          30       30              
  Lines        3870     4148     +278     
==========================================
+ Hits         3198     3446     +248     
- Misses        672      702      +30     

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[ernesto-at-fellow]

@sciyoshi @ericls @p7g
The new types for the transform module were added and this is ready for review. Once this is merged I'll update and prepare the PR for fellow.