[native] change outerRingSelectedColor prop type from string to ViewStyle

Summary:
Based on a comment I got on D7323 it would be better to have the outerRingSelectedColor prop type be a ViewStyle so that we can use a color entry from color.js instead of picking a color in the EmojiAvatarCreation component, which will help maintain a consistent design system

Depends on D7353

Test Plan:
Tested the selected color outer ring in ColorSelectors and EmojiAvatarCreation and got the following in light and dark mode:

ColorSelectors (does not use the outerRingSelectedColor prop):

Dark:

Light:

EmojiAvatarCreation: (used modalSubtext entry from colors.js as the outerRingSelectedColor prop)

Dark:

Light:

Reviewers: ashoat, atul

Reviewed By: ashoat

Subscribers: ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D7373