[native] Rename avatar action sheet actions
Summary:
Initially I just wanted to rename the "Reset to default" option for clarity, but ended up making several changes:
- Rename "Clear avatar" to "Reset to default" to avoid implying to the user that they can use Comm without an avatar
- In the "update avatar" flow, the verb "clear" makes more sense since it clears changes. In the registration flow, it seems more ambiguous... feels like it might imply that you can register without an avatar
- Be more consistent with capitalization
- Start each option with a verb for consistency
Test Plan: Flow
Reviewers: ginsu, atul
Reviewed By: ginsu
Subscribers: tomek
Differential Revision: https://phab.comm.dev/D8065