perf: Improve font cache perf

[eonarheim]

===:clipboard: PR Checklist :clipboard:===

• [ ] :pushpin: issue exists in github for these changes
• [ ] :microscope: existing tests still pass
• [ ] :see_no_evil: code conforms to the style guide
• [ ] :triangular_ruler: new tests written and passing / old tests updated with new scenario(s)
• [ ] :page_facing_up: changelog entry added (or not needed)

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This PR improves font cache perf by using numeric hashcodes instead of strings

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This PR hasn't had any recent activity lately and is being marked as stale automatically.

[eonarheim]

Closing for now