Move some stdlib tests from tests/ui to library/std/tests

[rytheo]

Related to #99417

[rustbot]

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[workingjubilee]

Thank you for the cleanup. One request:

[workingjubilee]

Please try to give an actual name to this test. What is it testing?

[rytheo]

I've updated the name and moved the description into the function's doc comment.

[workingjubilee]

Thank you!

@bors r+

[bors]

📌 Commit 1bec124 has been approved by workingjubilee

It is now in the queue for this repository.

[bors]

⌛ Testing commit 1bec124 with merge 8cef37d...

[bors]

☀️ Test successful - checks-actions
Approved by: workingjubilee
Pushing 8cef37d to master...

[rust-timer]

Finished benchmarking commit (8cef37d): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.3%	[-2.3%, -2.3%]	1
All ❌✅ (primary)	-	-	0

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 674.594s -> 676.654s (0.31%)
Artifact size: 315.87 MiB -> 315.91 MiB (0.01%)