Instead of grabbing `uname -vr` on non-Serenity platforms, let's just
hardcode a version. This prevents Lagom builds of applications like
Shell or Ladybird from reporting their version as that of the host OS.
We have a new, improved string type coming up in AK (OOM aware, no null
state), and while it's going to use UTF-8, the name UTF8String is a
mouthful - so let's free up the String name by renaming the existing
class.
Making the old one have an annoying name will hopefully also help with
quick adoption :^)
I've attempted to handle the errors gracefully where it was clear how to
do so, and simple, but a lot of this was just adding
`release_value_but_fixme_should_propagate_errors()` in places.
`ArgsParser` and `AboutDialog` had the same procedure to read the
version from `/res/version.ini`. Now they use the `SERENITY_VERSION`
string by default.
This commit refactored the version-reading utility to the new
`Core::Version` namespace.
