`AK::String` can now be reversed via AK::String::reverse(). This makes
life a lot easier for functions like `itoa()`, where the output
ends up being backwards. Very much not like the normal STL
(which requires an `std::reverse` object) way of doing things.
A call to reverse returns a new `AK::String` so as to not upset any
of the possible references to the same `StringImpl` shared between
Strings.
This was a workaround to be able to build on case-insensitive file
systems where it might get confused about <string.h> vs <String.h>.
Let's just not support building that way, so String.h can have an
objectively nicer name. :^)
Instead of aborting the program when we hit an assertion, just print a
message and keep going.
This allows us to write tests that provoke assertions on purpose.
