go.*,text,widget{,/material}: enable configurable line wrapping within words

This commit enables consumers of the text shaper to select a policy for how
line breaking candidates will be chosen. The new default policy can break lines
within "words" (UAX#14 segments) when words do not fit by themselves on a line.
This ensures that text does not horizontally overflow its bounding box unless
the available width is insufficient to display a single UAX#29 grapheme cluster.

Fixes: https://todo.sr.ht/~eliasnaur/gio/467
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>

text/lru.go

@@ -159,6 +159,7 @@ type layoutKey struct {
 	locale             system.Locale
 	font               giofont.Font
 	forceTruncate      bool
+	wrapPolicy         WrapPolicy
 }
 
 type pathKey struct {