Mark make_ascii_uppercase and make_ascii_lowercase in [u8] and str as const.

[bjoernager]

Relevant tracking issue: #130698

This PR extends #130697 and #130713 to the similar methods in byte slices ([u8]) and string slices (str).

For the str methods, this simply requires adding the const specifier to the function signatures. The [u8] methods, however, require (at least a temporary) reimplementation due to the use of iterators and for loops.

[rustbot]

r? @Amanieu

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[bjoernager]

@rustbot label +T-libs-api -T-libs

r? libs-api

[bjoernager]

No, what, how did I close this?!

[jhpratt]

@bors r+

[bors]

📌 Commit e723fe1 has been approved by jhpratt

It is now in the queue for this repository.

[bors]

⌛ Testing commit e723fe1 with merge 11e760b...

[bors]

☀️ Test successful - checks-actions
Approved by: jhpratt
Pushing 11e760b to master...

[rust-timer]

Finished benchmarking commit (11e760b): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was 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)	-0.3%	[-0.3%, -0.3%]	1
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 0.3%, secondary -1.4%)

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)	3.2%	[1.3%, 4.3%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-4.1%	[-5.2%, -2.9%]	2
Improvements ✅ (secondary)	-1.4%	[-1.4%, -1.4%]	1
All ❌✅ (primary)	0.3%	[-5.2%, 4.3%]	5

Cycles

Results (primary 0.4%)

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)	0.4%	[0.4%, 0.4%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.4%	[0.4%, 0.4%]	2

Binary size

Results (primary -0.2%)

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)	0.2%	[0.1%, 0.3%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.3%	[-0.6%, -0.0%]	8
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.2%	[-0.6%, 0.3%]	11

Bootstrap: 768.999s -> 770.84s (0.24%)
Artifact size: 340.87 MiB -> 340.88 MiB (0.00%)