Added support for beartype 0.17.0's __instancecheck_str__.

[patrick-kidger]

Recall that jaxtyping will currently generate rich error messages in precisely one scenario: about the arguments and return types when doing:

@jaxtyped(typechecker=beartype)
def foo(...): ...

With this commit we add support for beartype 0.17.0's pseudo-standard __instancecheck_str__, which allows us to report exactly why an instancecheck failed -- was the shape of the array wrong, was the dtype wrong, etc?

This means the following:

1. For those using beartype decorators, the following will also generate an informative error message, and moreover it will state exactly why (shape mismatch, dtype mismatch etc):

   @jaxtyped(typechecker=None)
   @beartype
   def foo(...): ...

   (In practice we probably won't recommend the above combination in the docs just to keep things simple.)

2. For those using the beartype import hook together with the jaxtyping import hook, we can probably also check assert isinstance(x, Float[Array, "foo"]) statements with rich error messages. (will runtime type checking go beyond function parameters and return type? #153) We'll need to test + document that though. (@jeezrick interested?)

3. For those using plain assert isinstance(...) statements without beartype (Provide a way to get error diagnostics out of isinstance checks #167, tagging @reinerp), then they can also get rich error messages by doing

   tt = Float[Array, "foo"]
   assert isinstance(x, tt), tt.__instancecheck_str__(x) + "\n" + print_bindings()

   which is still a bit long-winded right now but is a step in the right direction.

(CC @leycec for interest. Also CC @Qwlouse @Conchylicultor as I believe you're interested in this functionality.)

[leycec]

You build excitement. Thanks so much for the 0-day turnaround on this. Yet, I think to myself: "There's just no way he did this so fast. Is he even still human? I refuse to believe!" 😄

Let me know if you hit any snags with @beartype's __instancecheck_str__() implementation. In theory, everything works. In practice, I sigh.