Use Arbitrary Self Types instead of Py<Type>Methods traits

[LilyFoote]

For #4869.

I removed the Deref implementation for Bound<'py, T> because it conflicts with any implementation of std::ops::Receiver we need to use Arbitrary Self Types. For example:

error[E0119]: conflicting implementations of trait `std::ops::Receiver` for type `instance::Bound<'_, PyBool>`
  --> src/types/boolobject.rs:27:1
   |
27 | impl std::ops::Receiver for Bound<'_, PyBool> {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: conflicting implementation in crate `core`:
           - impl<P, T> std::ops::Receiver for P
             where <P as Deref>::Target == T, P: Deref, P: ?Sized, T: ?Sized;

I also added an implementation of PyAnyMethods for Bound<'py, T> to compensate for the removal of Deref. To get this working, I dropped the requirement that PyAnyMethods can only be implemented for sealed types. An alternative approach I think would be to just remove Deref and require .as_any() or .into_any() calls in more places.

After all of this, clippy passes on nightly on my machine (with the exception of one lint, which I think is unrelated to this PR). I can also run much of the test suite, but get an error in #[pyclass] which I currently don't understand:

error[E0599]: no method named `as_type_ptr` found for reference `&pyo3::Bound<'_, PyType>` in the current scope
 --> tests/test_field_cfg.rs:5:1
  |
5 | #[pyclass]
  | ^^^^^^^^^^
  |
  = note: this error originates in the attribute macro `pyclass` (in Nightly builds, run with -Z macro-backtrace for more info)
help: there is a method `as_ptr` with a similar name
  |
5 | as_ptr
  |

I'm confident this is coming from

pyo3/pyo3-macros-backend/src/pyclass.rs

Line 1834 in 29c64d8

.as_type_ptr()

but I see no reason why the .as_type_ptr method shouldn't be found, since it's implemented in

pyo3/src/types/typeobject.rs

Lines 51 to 54 in 29c64d8

	#[inline]
	pub fn as_type_ptr(self: &Bound<'py, Self>) -> *mut ffi::PyTypeObject {
	self.as_ptr() as *mut ffi::PyTypeObject
	}