rustdoc: Nuke --passes=list and defossilize the passes infrastructure

[fmease]

--passes and --no-defaults were deprecated and made noops years ago except that --passes list still prints all passes in a human-readable format as if users could still somehow make use of that information. Removing this useless functionality allows for some small simplifications (and longer term, it would enable us to further rewrite the way we represent internal passes w/o having to worry about it possibly affecting the CLI).

Given that the output of --passes list is clearly meant for human consumption only (I mean, just look at it), I hold the opinion that this removal doesn't need an FCP. And even if there were scripts somewhere out there that try to parse this output I think it would be okay to break them.

[rustbot]

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[fmease]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 219856d (219856d425ad6f2141b51eb0b9b957d0a98bbb8d, parent: ade84871f718ea20a6460d28e82290353b4bf3d2)

[rust-timer]

Finished benchmarking commit (219856d): comparison URL.

Overall result: ✅ improvements - no action needed

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

@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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.3%	[-0.3%, -0.3%]	1
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

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

Cycles

Results (primary 2.2%, secondary -0.7%)

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

	mean	range	count
Regressions ❌ (primary)	2.2%	[2.2%, 2.2%]	1
Regressions ❌ (secondary)	2.9%	[2.9%, 2.9%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.5%	[-2.5%, -2.4%]	2
All ❌✅ (primary)	2.2%	[2.2%, 2.2%]	1

Binary size

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

Bootstrap: 469.268s -> 472.628s (0.72%)
Artifact size: 388.12 MiB -> 388.15 MiB (0.01%)

[fmease]

@bors rollup-

[fmease]

ready