The issues is that the closure supplied to `request_measured_layout`
could be run multiple times with differing `known_dimensions`. This in
turn will mean we truncate the font runs once, inserting a multibyte
char at the end but then in the next iteration use those truncated runs
for possible the original untruncated string which has multibyte
characters overlapping the now truncated run end resulting in a faulty
utf8 boundary index.
Solution to this is simple, truncate a clone of the runs when needed
instead of modifying the original.
Fixes https://github.com/zed-industries/zed/issues/36925
Fixed ZED-2FF
Fixes ZED-2KM
Fixes ZED-2KK
Fixes ZED-1FF
Fixes ZED-255
Fixes ZED-2JD
Fixes ZED-2FX
Fixes ZED-2K2
Fixes ZED-2JX
Fixes ZED-2GE
Fixes ZED-2FC
Fixes ZED-2GD
Fixes ZED-2HY
Fixes ZED-2HR
Fixes ZED-2FN
Fixes ZED-2GT
Fixes ZED-2FK
Fixes ZED-2EY
Fixes ZED-27E
Fixes ZED-272
Fixes ZED-2EM
Fixes ZED-2CC
Fixes ZED-29V
Fixes ZED-25B
Fixes ZED-257
Fixes ZED-24R
Fixes ZED-24Q
Fixes ZED-23Z
Fixes ZED-227
Release Notes:
- Fixed a crash in text shaping when truncating rendered text