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.

Userland/Libraries/LibCore/Process.cpp

@@ -209,7 +209,7 @@ ErrorOr<bool> Process::is_being_debugged()
         auto const parts = line.split_view(':');
         if (parts.size() < 2 || parts[0] != "TracerPid"sv)
             continue;
-        auto tracer_pid = parts[1].to_uint<u32>();
+        auto tracer_pid = parts[1].to_number<u32>();
         return (tracer_pid != 0UL);
     }
     return false;