Add developer wallet features to fakewallet

[Michaelsulistio]

Context

fakewallet can be improved upon to make it the go-to Android wallet for developer testing MWA. This issue aims to track feature requests and ideas that can make fakewallet a more fleshed out developer wallet.

Motivations

• fakewallet loads much faster than a Phantom/Solflare which are prone to lag and crashing when using MWA on an emulator.

Ideas

• Persistent keypair storage so the wallet can be used consistently.
• Enable a way to import an existing keypair. Gradle settings or in-app import.
• Option to toggle fingerprinting/authentication
• Option to enable hot wallet mode and no authentication needed
• Transaction inspector UI during signing
  • Displays what transaction looks like, accounts, signers, what's going to be signed, etc
• An APK download link for easy installation, rather than cloning this repo and building from Android Studio

[Funkatronics]

We do have support for importing a private key into mwallet via a local gradle property. We could add that to fake wallet, but this still requires a dev to build the app from source.

[Funkatronics]

RE: transaction inspection. This is a technical challenge. We don't have the capacity to build this ourselves, but mwallet does support transaction simulation via Blowfish. The UI is super basic and could be expanded, but we will need to rely of Blowfish or a similar provider for the transaction sim.

I wont add this to fakewallet because that is beyond the scope of its purpose - testing MWA

[Funkatronics]

mwallet also supports fingerprint authentication FYI

We should separate these features into 2 categories: what is necessary for developing/testing an MWA implementation, and what is more for UX demonstration. Fakewallet should be reserved for testing only.

Items for FakeWallet (and likely mwallet as well):

• APK download for easy distribution
• maybe Private Key Injection (just private keys, not seed phrases)

Remaining items for mwallet only:

• Improve the transaction sim UI - the Blowfish infra is there we just need to expand what is shown on the UI
• Hot wallet mode - this will need to be an on the fly generated wallet. Any keys stored securely in the keystore require user authentication (pincode or fingerprint) to access. Tho maybe we could read the key out of storage and hold in memory for auto singing during the session.
• Persistent key storage (tho i think mwallet already has this)

[Michaelsulistio]

what is necessary for developing/testing an MWA implementation

IMO this should be the focus, so we can hold off on changes to mwallet.

As for the two changes to fakewallet, I agree with them. APK could even be distributed on a per-need basis rather than a hosted link.