[instant] Handle privacy mode in wallets

[BMillman19]

Description

• Make sure we are calling enable() on providers in situations where possible
• Remove the unused error AccountState

Testing instructions

Visit dogfood on coinbase wallet, current metamask, and old versions of metamask
http://0x-instant-dogfood.s3-website-us-east-1.amazonaws.com/

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• Prefix PR title with [WIP] if necessary.
• Prefix PR title with bracketed package name(s) corresponding to the changed package(s). For example: [sol-cov] Fixed bug.
• Add tests to cover changes as needed.
• Update documentation as needed.
• Add new entries to the relevant CHANGELOG.jsons.

[coveralls]

Coverage decreased (-0.009%) to 84.712% when pulling 38896c9 on feature/instant/privacy-mode into 26cbe7a on development.