make char::is_whitespace unstably const

[RalfJung]

I am adding this to the existing #132241 feature gate, since is_digit and is_whitespace seem similar enough that one can group them together.

[rustbot]

r? @cuviper

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[rustbot]

library/core/src/unicode/unicode_data.rs is generated by
src/tools/unicode-table-generator via ./x run src/tools/unicode-table-generator. If you want to modify unicode_data.rs,
please modify the tool then regenerate the library source file with the tool
instead of editing the library source file manually.

[ultrabear]

I went ahead and updated the tracking issue const_char_is_digit -> const_char_classify under the assumption that this is going to get merged

[jhpratt]

@bors r+ rollup

[bors]

📌 Commit 0804815 has been approved by jhpratt

It is now in the queue for this repository.

[bors]

⌛ Testing commit 0804815 with merge cf2b370...

[bors]

☀️ Test successful - checks-actions
Approved by: jhpratt
Pushing cf2b370 to master...

[rust-timer]

Finished benchmarking commit (cf2b370): 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 (primary -2.7%, secondary -3.4%)

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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.7%	[-3.4%, -2.3%]	3
Improvements ✅ (secondary)	-3.4%	[-3.4%, -3.4%]	1
All ❌✅ (primary)	-2.7%	[-3.4%, -2.3%]	3

Cycles

Results (secondary 0.8%)

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)	3.3%	[2.2%, 5.0%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-6.5%	[-6.5%, -6.5%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 782.184s -> 782.069s (-0.01%)
Artifact size: 335.25 MiB -> 335.27 MiB (0.01%)