add PyFloat::new_bound

[davidhewitt]

Part of #3684.

This implements PyFloat::new_bound, adds the deprecation warning to PyFloat::new, and migrates PyO3 code over to the new API.

[codspeed-hq]

CodSpeed Performance Report

Merging #3773 will degrade performances by 53.12%

_{Comparing davidhewitt:float-new-bound (345e122) with main (c54d897)}

Summary

⚡ 3 improvements
❌ 4 regressions
✅ 73 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	davidhewitt:float-new-bound	Change
❌	extract_float_extract_success	408.9 ns	464.4 ns	-11.96%
❌	extract_float_downcast_success	418.9 ns	474.4 ns	-11.71%
⚡	extract_int_downcast_fail	266.1 ns	238.3 ns	+11.66%
⚡	test_simple_py	34.7 µs	31.4 µs	+10.48%
❌	f64_from_pyobject	359.4 ns	766.7 ns	-53.12%
⚡	not_a_list_via_downcast	211.7 ns	183.9 ns	+15.11%
❌	list_via_downcast	157.2 ns	185 ns	-15.02%

[davidhewitt]

Thanks for the quick approval!

For what it's worth, the float benchmark regressions are not a surprise, ideally these will reverse once I update FromPyObject for f64 for #3706.