rustfmt use declarations

[nnethercote]

This PR implements rust-lang/compiler-team#750, which changes how use declarations are formatted by adding these options to rustfmt.toml:

group_imports = "StdExternalCrate"
imports_granularity = "Module"

r? @ghost

[rust-timer]

Finished benchmarking commit (2e63026): comparison URL.

Overall result: ❌ regressions - 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)	0.5%	[0.5%, 0.5%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.5%	[0.5%, 0.5%]	1

Max RSS (memory usage)

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

Cycles

Results (secondary -3.8%)

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)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.8%	[-3.8%, -3.8%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 767.825s -> 769.325s (0.20%)
Artifact size: 331.40 MiB -> 331.39 MiB (-0.00%)

[kornelski]

This has created a ton of merge conflicts, and most annoyingly it has undone #127090 which deliberately avoided rustfmt's brute naïveté to allow more than one options PR to coexist.

[nnethercote]

You can use #[rustfmt::skip] if you need it. I recommend adding explanatory comments alongside.

[tgross35]

This isn't especially noisy, but a .git-blame-ignore-revs entry might still be worth doing.

[nnethercote]

This isn't especially noisy, but a .git-blame-ignore-revs entry might still be worth doing.

Done in #128478.