Fixes dotnet#93008

This comes from F#, where interface method defined in F# doesn't have `newslot` flag in its metadata. Trimmer gets confused and doesn't recognize such method as a "base" method for its implementation in the type which implements the interface. As a result, the implementation method is removed from the program because there doesn't seem to be a use for it anywhere.

The fix is to basically ignore the `newslot` flag for interface instance methods. The existing behavior must be kept for static interface methods though - as a redefinition of a method with the `new` C# keyword will produce an interface method definition without the `newslot` flag as well.

The change adds a new test and modifies the AOT/analyzer infra to run the test as well.