Handle signing batches in the processor

Duplicates the existing signer for one tailored to batch signing.

processor/src/coins/bitcoin.rs

@@ -1,4 +1,8 @@
-use std::{io, collections::HashMap};
+use std::{
+  time::{SystemTime, Duration},
+  io,
+  collections::HashMap,
+};
 
 use async_trait::async_trait;
 
@@ -10,7 +14,7 @@ use frost::{
   ThresholdKeys,
 };
 
-use tokio::time::{Duration, sleep};
+use tokio::time::sleep;
 
 use bitcoin_serai::{
   bitcoin::{
@@ -197,6 +201,9 @@ impl BlockTrait<Bitcoin> for Block {
     hash.reverse();
     hash
   }
+  fn time(&self) -> SystemTime {
+    SystemTime::UNIX_EPOCH + Duration::from_secs(self.header.time.into())
+  }
   fn median_fee(&self) -> Fee {
     // TODO
     Fee(20)