add benchmark for class / method calls

[davidhewitt]

As a first step for #3843, let's add some benchmarks.

[codspeed-hq]

CodSpeed Performance Report

Merging #4016 will improve performances by 10.78%

_{Comparing davidhewitt:methods-benchmark (936851f) with main (74d9d23)}

Summary

⚡ 1 improvements
✅ 67 untouched benchmarks

🆕 4 new benchmarks

Benchmarks breakdown

	Benchmark	main	davidhewitt:methods-benchmark	Change
🆕	test_method_call	N/A	19.6 µs	N/A
🆕	test_method_call_py	N/A	19.7 µs	N/A
🆕	test_proto_call	N/A	18.7 µs	N/A
🆕	test_proto_call_py	N/A	19.8 µs	N/A
⚡	test_simple_py	28.9 µs	26 µs	+10.78%

[davidhewitt]

Now that I think about this more, probably the meaningful benchmark is to measure calling from Python. I'll move this to pytests later.

[davidhewitt]

As a small benchmark addition, I will just proceed to merge. I'd like to push a PR which uses this benchmark; having this in means codspeed will report if the PR actually makes a difference 👀