Add analyzers and code-fixes to help adoption of source-generated COM

[jkoritzinsky]

Fixes #86343

Also refactors a base class for our code-fixes to use that handles providing fix-all support and "enable allow unsafe blocks" support.

Interesting aspects here for the analyzer/fixer:

• We don't offer the fixer for interfaces that use arrays as the default array marshalling experience is different between built-in COM and source-generated COM.
• We don't offer the fixer for delegate types for the same reason.
• We do a very simple implementation for removing shadowing members where we remove any non-static interface method with the new keyword. We can try to make this smarter (validate members against base class, etc).
• We will need to have a corresponding (one-line) change in the SDK to expose the EnableComHosting property from MSBuild to Roslyn.

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Issue Details

---

Fixes #86343

Also refactors a base class for our code-fixes to use that handles providing fix-all support and "enable allow unsafe blocks" support.

Interesting aspects here for the analyzer/fixer:

• We don't offer the fixer for interfaces that use arrays as the default array marshalling experience is different between built-in COM and source-generated COM.
• We don't offer the fixer for delegate types for the same reason.
• We do a very simple implementation for removing shadowing members where we remove any non-static interface method with the new keyword. We can try to make this smarter (validate members against base class, etc).
• We will need to have a corresponding (one-line) change in the SDK to expose the EnableComHosting property from MSBuild to Roslyn.

Author:	jkoritzinsky
Assignees:	-
Labels:	area-System.Runtime.InteropServices
Milestone:	8.0.0

[jkoritzinsky]

Test failures are all known.