Reduce the tokio runtime worker thread count

There's really no reason why we need a lot of tokio threads - we
don't really do anything CPU-intensive and we expect Orange SDK
users to be "edge-nodes" that don't have a lot of channels.

Thus, spinning up a thread per CPU core wastes a good bit of memory
allocating stacks for threads we'll never use. Instead, just fix
the worker thread count to two.

Author: Matt Corallo

orange-sdk/src/ffi/orange/wallet.rs

@@ -125,7 +125,9 @@ pub struct Wallet {
 impl Wallet {
 	#[uniffi::constructor]
 	pub async fn new(config: WalletConfig) -> Result<Self, InitFailure> {
-		let rt = Arc::new(tokio::runtime::Builder::new_multi_thread().enable_all().build()?);
+		let rt = Arc::new(
+			tokio::runtime::Builder::new_multi_thread().worker_threads(2).enable_all().build()?,
+		);
 
 		let config: OrangeWalletConfig = config.try_into()?;