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.
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