Fixes formatting of owned entity type property names. These are normally named "FooBar_Baz" by EF Core, but the snake case thing was turning them into "foo_bar__baz". The double underscore is now fixed.
We don't *yet* have any EF Core owned entity in use, but I am planning to add one. I don't know if downstreams are using any so this should still be marked as a breaking change.
Also fixed it creating and dropping a Compiled Regex instance for every name, the regex is now cached (and pregenerated).
