Fix VSMEF008 to emit fully-qualified type names in diagnostic messages

[Copilot]

VSMEF008 diagnostic messages were showing only short type names, making it hard to identify which types were involved when names collide across namespaces.

Before:

warning VSMEF008: The contract type "SVsServiceProvider" is not assignable to the member type "IAsyncServiceProvider". The import may fail at runtime.

After:

warning VSMEF008: The contract type "Microsoft.VisualStudio.Shell.Interop.SVsServiceProvider" is not assignable to the member type "Microsoft.VisualStudio.Shell.IAsyncServiceProvider". The import may fail at runtime.

Changes

• VSMEF008ImportContractTypeMismatchAnalyzer.cs: Replaced SymbolDisplayFormat.CSharpShortErrorMessageFormat with the existing FullyQualifiedTypeNameFormat (which uses NameAndContainingTypesAndNamespaces) when formatting both type arguments in the diagnostic message.
• VSMEF008ImportContractTypeMismatchAnalyzerTests.cs: Added DiagnosticMessage_UsesFullyQualifiedTypeNames test that asserts diagnostic arguments contain namespace-qualified names.

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[Copilot]

Pull request overview

Improves the usefulness of the VSMEF008 analyzer diagnostic by emitting namespace-qualified type names in the diagnostic message, reducing ambiguity when short type names collide across namespaces.

Changes:

• Updated VSMEF008 analyzer to format both contract/member types using the existing FullyQualifiedTypeNameFormat.
• Added a regression test asserting VSMEF008 diagnostic arguments contain namespace-qualified type names.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Microsoft.VisualStudio.Composition.Analyzers/VSMEF008ImportContractTypeMismatchAnalyzer.cs	Switches diagnostic type formatting to a namespace-qualified SymbolDisplayFormat.
test/Microsoft.VisualStudio.Composition.Analyzers.Tests/VSMEF008ImportContractTypeMismatchAnalyzerTests.cs	Adds a test validating the diagnostic message arguments use fully qualified type names.