With this commit, <AK/Format.h> has a more supportive role and isn't
used directly.
Essentially, there now is a public 'vformat' function ('v' for vector)
which takes already type erased parameters. The name is choosen to
indicate that this function behaves similar to C-style functions taking
a va_list equivalent.
The interface for frontend users are now 'String::formatted' and
'StringBuilder::appendff'.
Two things I hate about C++:
1. 'int', 'signed int' and 'unsigned int' are two distinct types while
'char, 'signed char' and 'unsigned char' are *three* distinct types.
This is because 'signed int' is an alias for 'int' but 'signed char'
can't be an alias for 'char' because on some weird systems 'char' is
unsigned.
One might think why not do it the other way around, make 'int' an
alias for 'signed int' and 'char' an alias for whatever that is on
the platform, or make 'char' signed on all platforms. But who am I
to ask?
2. 'unsigned long' and 'unsigned long long' are always different types,
even if both are 64 bit numbers.
This commit fixes a few bugs that coming from this.
See Also: 1b3169f405.
This function is not avaliable in the kernel.
In the future it would be nice to have some sort of <charconv> header
that does this for all integer types and then call it in strtoull and et
cetera.
The difference would be that this function say 'from_chars' would return
an Optional and not just interpret anything invalid as zero.
