Follow-ups to "Refactor fbp workspace management" (#82509)

I think we discussed that MiscellaneousFileWithNoReferences doesn't really make much sense as a state -- in that case it'd be good to delete this. I think you had a follow up on that?

_Originally posted by @jasonmalinowski in https://github.com/dotnet/roslyn/pull/82509#discussion_r2956914908_

@dibarbet:
> I think it makes sense for the option, but I am OK with removing that option (and just having the FBP one).

@RikkiGibson:
> I think that at minimum the helper `ClassifyAsMiscellaneousFileWithNoReferences` makes sense to have. The reason we wouldn't want to have it here is: we can't make `ProjectFileInfo` for `MiscellaneousFileWithNoReferences`. It's too painful to maintain both that and the existing path that produces `ProjectInfo`.
>
> I'm going to file a follow-up for cleaning this up.

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To call this out, since you had that issue with the project path being not a "real" path -- this is setting the path of a project as created in the workspace. This may be unnecessary to set and instead could be overridden to null.

_Originally posted by @jasonmalinowski in https://github.com/dotnet/roslyn/pull/82509#discussion_r2956836462_

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- [ ] Delete extra debug logging from the canonical provider
- [ ] Try putting back the new TargetFramework variable into canonical project XML