[native] Make reanimated code in account modals more readable

Summary:
Following up from this review comment, I:

1. Added some variable names for some of the confusing constants
2. Updated the code to avoid using number literals for mode numbers, relying instead of the modeNumbers object
3. Updated the code to avoid comparing mode numbers

Reviewers: palys-swm

Reviewed By: palys-swm

Subscribers: KatPo, zrebcu411, Adrian

Differential Revision: https://phabricator.ashoat.com/D54