Foundation URL Improvements

[Max_Desiatov]

@icharleshu

Because this initializer takes a StaticString known at compile-time, it considers "schemeless" String s as a programmer error and assert s the existence of a scheme. It will also assert any invalid web addresses, which mainly means empty strings and strings with invalid characters.

Do I understand correctly that these are runtime assertions? Thus URL("invalid URL") would still compile and type-check as non-optional URL without any compile-time errors?