Refactor font rendering pipeline, remove `font-kit` and `pathfinder` #492

Job	Run time
test_all_features_exclude_ab_glyph	1m 28s
cargo-doc	45s
msrv	33s
build_and_test (ubuntu-latest)	1m 52s
run_all_examples	2m 13s
build_and_test (macos-latest)	1m 59s
build_and_test (windows-latest)	3m 8s
test_all_features_exclude_doctests	1m 9s
	13m 7s

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