raw_path should not be Optional

[nggit]

The reason raw_path is purely what the client sends, it's not ambiguous.

While path tends to have various assumptions, whether %2f should be decoded or not, percent-encoding contains utf-8 or what, is it true that decoding by forcing utf-8 is guaranteed valid or not? etc.

Applications are better off relying on raw_path to avoid the unpredictable consequences, bugs, etc. if they rely on path.

Also, I find this reasoning is nonsensical:

Some web server implementations may be unable to provide this

https://asgi.readthedocs.io/en/latest/specs/www.html#http-connection-scope

[carltongibson]

The history here is on #87.