[Cashtab] Deprecate hooks directory and move hooks to where they are used

Summary:
Doesn't really make sense that useWallet is not in src/wallet. Likewise, useWindowDimensions is only used by Receive. It might make sense to move that to helpers later but for now it's just a Receive thing.

Get rid of now-empty hooks folder which is not really useful organization.

Test Plan: npm test, grep -r "hooks/useWallet" src/ and no output

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D15864