A Devanagari fuzz input that GSUB grows to 3,079 glyphs takes about 24 s #302

Found while fuzzing #301 (and present on main before it): a Devanagari input from the shape fuzz target, which GSUB grows to 3,079 glyphs, takes about 24 s per run in a fuzz build on main (23.5 to 24.7 s; 32 to 35 s with #301's target, which shapes every input twice).

To do:

• Reproduce from the fuzz artifact (the Bound the shaping caches' work and memory on hostile fonts #301 author's scratch logs are in the coordinator's job folder; rerunning the shape target with the Devanagari seeds should find it again).
• Measure a release build and HarfBuzz 14.5.0 on the same font and text.
• Find which stage grows or walks the buffer super-linearly (the syllabic reordering, a GSUB loop that keeps inserting glyphs within HarfBuzz's max-len/max-ops limits, or position passes over a long buffer), and bound it the way HarfBuzz's max_len and max_ops do.