Everywhere: Use to_number<T> instead of to_{int,uint,float,double}

In a bunch of cases, this actually ends up simplifying the code as
to_number will handle something such as:

```
Optional<I> opt;
if constexpr (IsSigned<I>)
    opt = view.to_int<I>();
else
    opt = view.to_uint<I>();
```

For us.

The main goal here however is to have a single generic number conversion
API between all of the String classes.

Meta/Lagom/Tools/CodeGenerators/StateMachineGenerator/main.cpp

@@ -92,7 +92,7 @@ parse_state_machine(StringView input)
             if (lexer.next_is('\\')) {
                 num = (int)lexer.consume_escaped_character('\\');
             } else {
-                num = lexer.consume_until('\'').to_int().value();
+                num = lexer.consume_until('\'').to_number<int>().value();
                 lexer.ignore();
             }
             lexer.consume_specific('\'');