bisect: don't require Sequences

[Rogdham]

This PR changes the type of the first argument of bisect_left and bisect_right (and by design bisect as well) from the bisect module.

Indeed, a full Sequence is not needed, only the following is needed:

• If the hi parameter is None, only __getitem__ and __len__
• Else, only __getitem__

I'm asking for SupportsLenAndGetItem instead of only SupportsGetItem in the second case to avoid an exponential number of @overload.

---

You can check that only these attributes are needed with the following code:

from bisect import bisect, bisect_left, bisect_right


class Minimal:
    content = 'abbbbcd'

    def __len__(self):
        return len(self.content)
    
    def __getitem__(self, pos):
        return self.content[pos]

obj = Minimal()

assert bisect(obj, 'b') == 5
assert bisect_left(obj, 'b') == 1
assert bisect_right(obj, 'b') == 5

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[JelleZijlstra]

It's a bit more complicated because it uses the C sequence protocol and therefore doesn't allow e.g. dicts, but I don't think we need to try to express that in the stub.

[Rogdham]

Thank you!