Bitcoin wallet (Bitcoin Integration Rust sample dApp)

[BenjaminLoison]

[ER-2524] Build Bitcoin Integration Sample Dapp

The Bitcoin integration feature, as the core feature of the Chromium release, must come with an engaging sample dapp. The goal is to build a functional Bitcoin wallet as a sample dapp. Users must be able to 1. Sign into the wallet using Internet Identity 2. View their balance ~~and transaction history~~ 3. Send Bitcoin to another address A graphical overview of the sample dapp is provided here.

@THLO @ielashi @olaszakos