Fail the tests when an analyzer throws

[meziantou]

Fixes #1331

What changed

VerifyDiagnosticResults filters the actual diagnostics by the configured default rule id before counting them. Roslyn surfaces an analyzer exception as an AD0001 diagnostic with Location.None: GetSortedDiagnosticsFromDocuments did add it to the list, and this filter then discarded it. In a test that expects zero diagnostics, expected and actual were both 0 and the test was green even though the analyzer threw.

The harness now passes CompilationWithAnalyzersOptions with an onAnalyzerException handler that records the exception, and AssertNoAnalyzerException fails right after GetAnalyzerDiagnosticsAsync — before the DefaultAnalyzerId filter, before sorting, and on the code fix paths too, as all of them go through GetSortedDiagnosticsFromDocuments. The failure message contains the analyzer type and the full exception with its stack trace, which is more actionable than the AD0001 message. A check on the AD0001 diagnostics remains as a safety net in case Roslyn ever reports a failure without invoking the handler.

VerifyDiagnostic_ReportsAnalyzerException covers it: an analyzer that throws, registered with id: so the DefaultAnalyzerId filtering is active, and no expected diagnostic — the exact shape that was silently green before.

Verification

• dotnet test --max-parallel-test-modules 2: 18789 passed, 0 failed, for the 5 Roslyn versions (4.8, 4.14, 5.0, 5.6, 5.9). The CompilationWithAnalyzersOptions constructor overload works on 4.8.
• No pre-existing crash surfaced: the two issues filed alongside are already fixed on main (60df5ba, c6054ab).
• dotnet run --project src/DocumentationGenerator exits 0 and does not change any markdown file, as this is a test-only change.

Not included: the same filter hiding a second rule

The issue also mentions that the DefaultAnalyzerId filter hides a wrong second rule from the multi-descriptor analyzers. Removing the filter breaks 27 tests on roslyn5.9: OptimizeLinqUsageAnalyzer (12), UseStringComparisonAnalyzer (5), UseLangwordInXmlComment (3), ConcurrentDictionaryMustPreventClosureWhenAccessingTheKey (3), and 4 others. Each one needs a decision on whether the second diagnostic is expected or a false positive, so this PR leaves it out rather than blanket-annotating them. Happy to do it in a follow-up.