Get rid of the weird old signature:
- int StringType::to_int(bool& ok) const
And replace it with sensible new signature:
- Optional<int> StringType::to_int() const
`read_bool_entry()` can now interpret both integers (1 or 0) and
Boolean strings ("true" or "false") in configuration files.
All values other than "1" or "true" are considered false.
Previously, this function was using `AK::String::to_uint()`, which is
wrong considering the function returns type `int`. This also means that
configuration files would revert to the default value on negative
values.
