resolve: Make sure visibilities of import declarations make sense

[petrochenkov]

That they are all ordered inside the module and not more private than the module itself.

The import_decl_vis logic is also reused when reporting ambiguous_import_visibilities lint.
Some asserts are hardened.
Some relevant tests are added.

Extracted from #154149.

[rustbot]

r? @jdonszelmann

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[petrochenkov]

cc @yaahc

[petrochenkov]

To make sure the asserts are not expensive.
@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 89a90f3 (89a90f39ff9b6aadf1ca3a80a26c38deb2592682, parent: 14196dbfa3eb7c30195251eac092b1b86c8a2d84)

[rust-timer]

Finished benchmarking commit (89a90f3): comparison URL.

Overall result: no relevant changes - 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
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

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

Max RSS (memory usage)

Results (primary 1.5%, secondary -6.7%)

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

	mean	range	count
Regressions ❌ (primary)	1.5%	[1.5%, 1.5%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-6.7%	[-6.7%, -6.7%]	1
All ❌✅ (primary)	1.5%	[1.5%, 1.5%]	1

Cycles

Results (primary -2.6%, secondary 11.4%)

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)	11.4%	[2.7%, 25.8%]	3
Improvements ✅ (primary)	-2.6%	[-3.0%, -2.3%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.6%	[-3.0%, -2.3%]	2

Binary size

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

Bootstrap: 491.114s -> 490.825s (-0.06%)
Artifact size: 394.23 MiB -> 394.30 MiB (0.02%)

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.