Extract the typeface-finding logic to `findEffectiveTypeface`

[cubuspl42]

Summary:

Extract the typeface-finding logic to findEffectiveTypeface extension methods.

Changelog:

[INTERNAL] [CHANGED] - Extract the typeface-finding logic to findEffectiveTypeface

Test Plan:

[cubuspl42]

This is not a very big deal, but helps me later down the road in my work on https://github.com/facebook/react-native/issues/42602

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	17,066,844	+12
android	hermes	armeabi-v7a	n/a	--
android	hermes	x86	n/a	--
android	hermes	x86_64	n/a	--
android	jsc	arm64-v8a	20,450,434	+2
android	jsc	armeabi-v7a	n/a	--
android	jsc	x86	n/a	--
android	jsc	x86_64	n/a	--

Base commit: cfc0ba04a1fa147517e94d1f952e2a8fe62e6e9c Branch: main