Propagate #[allow(dead_code)] on adts to their inherent impls

[mu001999]

This PR does:

1. propagate #[allow(dead_code)] on adts to their inherent impls and impl items
2. refactor the previous implementation in Impls and impl items inherit dead_code lint level of the corresponding traits and trait items #144113

Fixes #149142

[mu001999]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 25aedf1 (25aedf1c569cd8fb010ed559082eacf12d56aaa2, parent: 3daae5e42ec9ba435212987331af1b7b8634fa90)

[rust-timer]

Finished benchmarking commit (25aedf1): comparison URL.

Overall result: ❌ regressions - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never
@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)	0.5%	[0.1%, 0.9%]	52
Regressions ❌ (secondary)	0.4%	[0.2%, 0.7%]	16
Improvements ✅ (primary)	-0.2%	[-0.2%, -0.2%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.5%	[-0.2%, 0.9%]	53

Max RSS (memory usage)

Results (primary -2.3%, secondary -1.0%)

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

	mean	range	count
Regressions ❌ (primary)	2.3%	[2.3%, 2.3%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-3.9%	[-6.9%, -0.9%]	3
Improvements ✅ (secondary)	-1.0%	[-1.0%, -1.0%]	1
All ❌✅ (primary)	-2.3%	[-6.9%, 2.3%]	4

Cycles

Results (secondary 21.3%)

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

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	21.3%	[20.3%, 22.4%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 519.503s -> 518.599s (-0.17%)
Artifact size: 401.51 MiB -> 401.51 MiB (-0.00%)