Check if AttributeData for InterfaceTypeAttribute is not null in ConvertComImportToGeneratedComInterfaceAnalyzer

[mpidash]

ConvertComImportToGeneratedComInterfaceAnalyzer always assumed that an InterfaceTypeAttribute was present on interface types with ComImportAttribute, throwing a NullReferenceException if it was missing.
This PR also adds tests for each unsupported ComInterfaceType.

Not sure why there was no nullability warning in the original code.

Fixes #94968.

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Issue Details

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ConvertComImportToGeneratedComInterfaceAnalyzer always assumed that an InterfaceTypeAttribute was present on interface types with ComImportAttribute, throwing a NullReferenceException if it was missing.
This PR also adds tests for each unsupported ComInterfaceType.

Not sure why there was no nullability warning in the original code.

Fixes #94968.

Author:	mpidash
Assignees:	-
Labels:	area-System.Runtime.InteropServices
Milestone:	-

[elinor-fung]

@jkoritzinsky would this be worth backporting, since it is affecting VS editing experience?

[jkoritzinsky]

I think it's worthwhile to backport.

[jkoritzinsky]

/backport to release/8.0-staging

[github-actions]

Started backporting to release/8.0-staging: https://github.com/dotnet/runtime/actions/runs/8025295750