Reformat imports to a consistent style for imports

rustfmt.toml configuration:
  imports_granularity = "One"
  group_imports = "One"

sdk/src/signer/mod.rs

@@ -100,8 +100,7 @@ pub fn unique_signers(signers: Vec<&dyn Signer>) -> Vec<&dyn Signer> {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
-    use crate::signer::keypair::Keypair;
+    use {super::*, crate::signer::keypair::Keypair};
 
     fn pubkeys(signers: &[&dyn Signer]) -> Vec<Pubkey> {
         signers.iter().map(|x| x.pubkey()).collect()

sdk/src/signer/presigner.rs

@@ -63,8 +63,7 @@ where
 
 #[cfg(test)]
 mod tests {
-    use super::*;
-    use crate::signer::keypair::keypair_from_seed;
+    use {super::*, crate::signer::keypair::keypair_from_seed};
 
     #[test]
     fn test_presigner() {