Update TypeProvider

[live1206]

Needed for Azure/azure-sdk-for-net#47665

• Update modifiers of TypeProvider
• Update relativeFilePath of TypeProvdier
• remove sealed from ModelProvider, so that ResourceDataProvdier in Azure plugin can share most of the existing logic

[azure-sdk]

API change check

APIView has identified API level changes in this PR and created following API reviews.

Microsoft.Generator.CSharp

[ArcturusZhang]

shall we consider to make the stringextensions as shared file that is imported by azure plugin?
maybe not quite a good idea but we could consider if we prefer not making it public

[live1206]

shall we consider to make the stringextensions as shared file that is imported by azure plugin? maybe not quite a good idea but we could consider if we prefer not making it public

Since importing StringExtensions to Azure plugin is across-repo, we need to maintain additional scripts or manual effort to update it to latest.

Not sure about the reasons of not making it public, I will hold the merge until we get this clarified.
cc @JoshLove-msft

[live1206]

shall we consider to make the stringextensions as shared file that is imported by azure plugin? maybe not quite a good idea but we could consider if we prefer not making it public

Offline synced with @JoshLove-msft, we should not have public APIs that are extension methods of BCL types. And we don't need the String.ToCleanName() method in ResourceDataProvider for now.
Revert the change and expose public static methods instead of extension methods until we really need them.