Generalise (most) impls on Box

[nia-e]

Resolves the trait impl concern for #156882; Default wasn't touched since changing that would be breaking, but hopefully all of this should be fine - I'll do a crater run to be sure. Certain impls that were for one reason or another Annoying to generalise (e.g. Clone for Box<Path>) were also untouched since I believe we can add those in the future, as they're on concrete types.

r? clarfonthey

[nia-e]

also should do a perf run since monomorphisation.

@bors try @rust-timer queue

[clarfonthey]

r=me pending crater + perf

[rust-bors]

☀️ Try build successful (CI)
Build commit: 0c3b2c2 (0c3b2c226322b623e493b7611e4909ee6bc6a48d)
Base parent: 344f790 (344f7902949345394fa40a5d7dda31f012ccbc0d)

[nia-e]

@craterbot check

[craterbot]

👌 Experiment pr-161946 created and queued.
🤖 Automatically detected try build 0c3b2c2
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[rust-timer]

Finished benchmarking commit (0c3b2c2): comparison URL.

Overall result: ❌✅ regressions and improvements - no action needed

Benchmarking means the PR may be perf-sensitive. Consider adding rollup=never if this change is not fit for rolling up.

@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.4%	[0.4%, 0.4%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.5%	[-0.5%, -0.5%]	1
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 3.2%, secondary -0.3%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	9.0%	[9.0%, 9.0%]	1
Regressions ❌ (secondary)	4.1%	[1.6%, 8.7%]	5
Improvements ✅ (primary)	-2.6%	[-2.6%, -2.6%]	1
Improvements ✅ (secondary)	-4.6%	[-5.7%, -2.4%]	5
All ❌✅ (primary)	3.2%	[-2.6%, 9.0%]	2

Cycles

Results (primary 2.7%, secondary -11.8%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	2.7%	[2.7%, 2.7%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-11.8%	[-20.6%, -3.9%]	7
All ❌✅ (primary)	2.7%	[2.7%, 2.7%]	1

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 475.673s -> 475.454s (-0.05%)
Artifact size: 403.60 MiB -> 402.86 MiB (-0.18%)

[nia-e]

that's a nothingburger, nice. time to just wait a zillion years for crater lol