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'.
We will now actually use MIME types for clipboard. The default type is now
"text/plain" (instead of just "text").
This also fixes some issues in copy(1) and paste(1).
This commit moves the clipboard from WindowServer into a new Clipboard
service program. Clipboard runs as the unprivileged "clipboard" user
and with a much tighter pledge than WindowServer.
To keep things working as before, all GUI::Application users now make
a connection to Clipboard after making the connection to WindowServer.
It could be interesting to connect to Clipboard on demand, but right
now that would necessitate expanding every GUI app's pledge to include
"unix" and also unveiling the clipboard portal, which I prefer not to.
