Add Regtest Setup and Tests in CI

[thunderbiscuit]

This PR brings in a Regtest Infinity Pro in our CI test workflow and runs a Kyoto sync test using it.

This is done using a new library I've been working on called regtest-toolbox which provides utilities for speaking to a regtest environment easily, including sending coins and mining blocks, which we use here. The test now simply uses the following:

val regtestEnv = RegEnv.connectTo(walletName = "faucet", username = "regtest", password = "password")

val wallet: Wallet = Wallet.createSingle()
val newAddress = wallet.revealNextAddress(KeychainKind.EXTERNAL).address

regtestEnv.send(
    address = newAddress.toString(), 
    amount = 0.12345678, 
    feeRate = 2.0
)
regtestEnv.mine(2)

[thunderbiscuit]

The new test here will fail because of a small bug in the latest bdk_kyoto lib, but the fix is here: bitcoindevkit/bdk-ffi#953.

You can see that the test passes by bumping bdk_kyoto to 0.15.4 locally in your bdk-ffi/bdk-ffi/Cargo.toml file.

[thunderbiscuit]

Note that once I get an ACK on this I'll drop the commit that changes the bdk-ffi submodule as that's not something I intend to merge; I just wanted to show that the CI can pass using this new regtest setup.

[ItoroD]

This is great!

ACK 92f95c6