Use pango to parse font configuration early, and reject the command as
invalid if the value is invalid for pango. Since we're already parsing
the font into a `PangoFontDescription`, keep that instance around and
avoid re-parsing the font each time we render text.
Fixes: https://github.com/swaywm/sway/issues/6805
Use fixed titlebar heights. The default height is calculated based on
font metrics for the configured font and current locale.
Some testing with titles with emoji and CJK characters (which are
substantially higher in my setup) shows that the titlebars retain their
initial value, text does shift up or down, and all titlebars always
remain aligned.
Also drop some also now-unecessary title_height calculations.
Makes also needed to be updated, since they should be positioned with
the same rules.
Patch tested by compiling with `__attribute__ ((format (printf, 2, 3)))`
applied to `cmd_results_new`.
String usage constants have been converted from pointers to arrays when
encountered. General handler format strings were sometimes modified to
include the old input string, especially for unknown command errors.
