introduce fast path to LazyTypeObject::get_or_init

[davidhewitt]

Split from #5223, because this part of the refactor is worth pulling out and highlighting as a perf improvement (I think).

[codspeed-hq]

CodSpeed Performance Report

Merging #5324 will degrade performances by 12.85%

_{Comparing davidhewitt:type-object-fast-path (03334ff) with main (15045db)}

Summary

⚡ 2 improvements
❌ 1 regressions
✅ 92 untouched benchmarks

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

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	ordered_dunder_methods	3.1 µs	2.8 µs	+11.97%
⚡	ordered_richcmp	3.2 µs	2.6 µs	+20.94%
❌	extract_float_cast_fail	395.6 ns	453.9 ns	-12.85%

[davidhewitt]

Seems flaky on downloads, will keep retrying 🤔

[Icxolu]

Looks like we're not the only ones hitting this currently: https://rust-lang.zulipchat.com/#narrow/channel/242791-t-infra/topic/Channel.20manifest.20downloads.20timeout.20in.20GHA