Fix various c++ warnings

[acoates-ms]

Summary

react-native-windows runs with a more strict set of warnings as errors. This fixes a bunch of warnings being hit while compiling core react-native code as part of react-native-windows. In particular warnings about mismatched signed/unsigned comparisons, lossy conversions, and variable names that conflict with names in outer scopes (yoga has a global for leading and trailing that conflicts with some local variable names)

Changelog

[Internal] [Fixed] - Fix various C++ warnings

Test Plan

I've run these changes in react-native-windows. -- Shouldn't have any functionality difference.

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	8,855,108	+897
android	hermes	armeabi-v7a	8,375,477	-214
android	hermes	x86	9,310,979	-248
android	hermes	x86_64	9,254,165	+77
android	jsc	arm64-v8a	10,586,055	+936
android	jsc	armeabi-v7a	10,089,531	-176
android	jsc	x86	10,603,420	-208
android	jsc	x86_64	11,186,876	+108

Base commit: ca8a755

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
ios	-	universal	n/a	--

Base commit: 2c34946

[facebook-github-bot]

@rozele has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[facebook-github-bot]

@rozele merged this pull request in 4d87d8c.