Compile times

I've just been looking into compile times for Blitz. And `read-fonts` (16.14s) and `skrifa` (9.61s) both stand out in the profile. This is for a release build:


This mostly gets hidden by parallel compilation (the non-codegen times are not nearly so bad). And perhaps this is the only way to get the runtime performance and type safety of this crate. But nevertheless I though this should be tracked, and considered when implementing changes to these crates.

(note also the compile time for `ttf-parser` at the bottom of the screenshot - only 5.5s!)

Start by reproducing the release-build compile profile described in the issue and inspect the reported read-fonts and skrifa times, with ttf-parser as the comparison point. The issue names no files or tests and gives no acceptance criteria, so completion would need to be defined before implementation.

Written by the indexing model from the issue text.