Performance optimization for dataclass order methods

[gesslerpd]

Similar to #104904

This can speed up ordering/comparison operations by ~2x by making the comparison similar to existing __eq__ performance.

Benchmark timings for classes with 5 integer fields:

	equality (ms)	order (ms)
standard class w/ optimization	46.19	47.27
existing dataclasses	45.96	114.22

[AA-Turner]

Don't use a PR number as the issue prefix, things get confused. Please can you create an issue for this PR, and add a NEWS entry?

Please can you use a pyperformance benchmark, and update the PR with the benchmark code and results? Microbenchmark results should show a reasonably large performance improvement, which this PR hopefully will based on the preliminary numbers you've shown.

A

[ericvsmith]

We need to be very careful that we're not changing semantics with this. We've had that problem before with comparisons (although of course now I can't find the issue). I don't think we added tests for this, because we didn't find the problem until after we'd released the code.

[gesslerpd]

@ericvsmith so we need set of tests that pass prior to this change?

Potentially relevant "semantics" you mention may be shown in the tests for this change in #582?