feat: add __dask_tokenize__ hook

[lgray]

This is related to dask/dask#10918

In particular with dask/dask#10883 even those changes don't fix everything.

This at least makes it so that only shape is touched in the present error and with future changes.

This rest is that array.layout.form touches shape.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 81.93%. Comparing base (b749e49) to head (1e7c09b).
Report is 36 commits behind head on main.

Additional details and impacted files

Files	Coverage Δ
src/awkward/highlevel.py	76.59% <50.00%> (-0.08%)	⬇️

... and 4 files with indirect coverage changes

[lgray]

Just to link to the wider discussion: dask-contrib/dask-awkward#468

[agoose77]

@lgray is this still a direction worth pursuing?

[lgray]

Yes it is still useful in case people are sticking awkward arrays directly in the graph.

[agoose77]

Then I think we can merge this. Are there any tests in dask-awkward?

[lgray]

Since the operation I mentioned is something you do outside of dask awkward there are no tests in dask awkward for it.

[agoose77]

@lgray hmm, fair. We can add tests here to check this, then :) Leave it to me ...

[jpivarski]

This was accepted, but somehow missed getting merged. I'll merge it now.