Fix crash that happens with shadow color with 0 alpha (#46551)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/46551

We crash if we pass a shadow color with 0 alpha due to some divide by 0 logic. This fixes that for inset and outset shadows and adds a test for that case.

Changelog: [Internal]

Reviewed By: NickGerleman

Differential Revision: D62899047

fbshipit-source-id: 2aff1d016dd97bed024df1c3f89bcc62e49f0306