Annotate AnalysisLevel property

[gewarren]

The AnalysisLevel property seems to be shared between C# compiler messages and Roslyn code analysis. I'll log an issue to make note of this in the code analysis and C# compiler options docs.

We also might want to update the verbiage around CodeAnalysisRuleSet since rulesets are deprecated in favor of .editorconfig files.

Originally posted by @gewarren in #29498 (comment)

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Document Details

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• ID: 26ef35c2-6df4-26f8-32b2-9b50eb76c037
• Version Independent ID: e57ac82b-307e-163b-8172-52644b3a6baa
• Content: C# Compiler Options - errors and warnings
• Content Source: docs/csharp/language-reference/compiler-options/errors-warnings.md
• Product: dotnet-csharp
• Technology: csharp-language-reference
• GitHub Login: @BillWagner
• Microsoft Alias: wiwagn

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Associated WorkItem - 436872

[Youssef1313]

There was a recent change in this area in dotnet/sdk#24826.

Old behavior was that AnalysisLevel overwrites WarningLevel. So WarningLevel wasn't taken into account if AnalysisLevel is set.

New behavior is AnalysisLevel sets WarningLevel only if the user didn't set WarningLevel himself.

cc @baronfel @jmarolf @mavasani

[baronfel]

Yep, we generally want defaults to only be set if the user hasn't set something, and thanks to @Youssef1313 we found a bug where we were unconditionally setting the WarningLevel. It's definitely been one of those issues' that's spiralled a bit past my initial expected size, though!

[BillWagner]

The docs currently describe the old behavior. See here.

When does the new behavior ship? And, is that going to change the Visual Studio option pages?o