Symbols: add Mfv.ApparentEnclosingType

[auduchinok]

Adds another way of getting extended type which allows inspecting extended type parameter types.

[github-actions[bot]]

:warning: Release notes required, but author opted out

[!WARNING] Author opted out of release notes, check is disabled for this pull request. cc @dotnet/fsharp-team-msft

[T-Gro]

Converted to draft until green, please mark as ready to review once this is ready to be merged.

[auduchinok]

@vzarytovskii Could someone from MS team look at the changes needed in Editor project, please?

[auduchinok]

This is ready 🙂