Fix missing glyph errors in gpu_cache and add benchmarks

Created by: alexheretic

Summary:

• Fixes for missing gpu cache glyphs
• Updated dependencies & example code
• gpu cache benchmarks & tests, run rustup run nightly cargo bench --features bench

Most of the details explained in #53 apply to this, including the performance. In addition to that PR I've:

• switched from support/* collections to rust std collections.
• fixed oldest_in_use_row unsound logic in cache_queued, this also caused missing glyphs.
• optimised cache_queued by using an unstable sort.

The benchmark figures have changed now a new font has been adopted. In fact a more complex font would probably be better to benchmark against and track regressions.

Fixes #52 (closed)