deeper rustc_builtin_macros cleanups

[cyrgani]

As a followup to #161464, this contains a few more surface cleanups and begins simplifying the mess that SubstructureFields currently is by removing the StaticFields type in favor of just using the VariantData directly.

[rustbot]

Changes to the code generated for builtin derived traits.

cc @nnethercote

[rustbot]

r? @adwinwhite

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The reviewer was selected based on:

• Owners of files modified in this PR: compiler
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[Kobzol]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: cc25c3c (cc25c3c8dae9c6546d9fdd11168f5e7c5715a163)
Base parent: e457a7b (e457a7b0d326d67b4322ef0d11bd715cfaeda48f)

[rust-timer]

Finished benchmarking commit (cc25c3c): comparison URL.

Overall result: ✅ improvements - no action needed

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.

@bors rollup=never rustc-perf
@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)	-0.2%	[-0.2%, -0.2%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.2%	[-0.2%, -0.2%]	3

Max RSS (memory usage)

Results (primary -1.0%, secondary -3.9%)

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)	-2.7%	[-3.1%, -2.3%]	2
Improvements ✅ (secondary)	-3.9%	[-6.3%, -1.5%]	2
All ❌✅ (primary)	-1.0%	[-3.1%, 2.3%]	3

Cycles

Results (primary -1.1%, 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)	2.0%	[2.0%, 2.0%]	1
Regressions ❌ (secondary)	2.7%	[2.7%, 2.7%]	1
Improvements ✅ (primary)	-2.1%	[-2.4%, -2.0%]	3
Improvements ✅ (secondary)	-2.1%	[-2.1%, -2.1%]	1
All ❌✅ (primary)	-1.1%	[-2.4%, 2.0%]	4

Binary size

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

Bootstrap: 476.343s -> 474.625s (-0.36%)
Artifact size: 402.74 MiB -> 402.73 MiB (-0.00%)