CLI: dynamic signing reboot (#8384)

* Add keypair_util_from_path helper

* Cli: impl config.keypair as a trait object

* SDK: Add Debug and PartialEq for dyn Signer

* ClapUtils: Arg parsing from pubkey+signers to Presigner

* Impl Signers for &dyn Signer collections

* CLI: Add helper for getting signers from args

* CLI: Replace SigningAuthority with Signer trait-objs

* CLI: Drop disused signers command field

* CLI: Drop redundant tests

* Add clap validator that handles all current signer types

* clap_utils: Factor Presigner resolution to helper

* SDK: `From` for boxing Signer implementors to trait objects

* SDK: Derive `Clone` for `Presigner`

* Remove panic

* Cli: dedup signers in transfer for remote-wallet ergonomics

* Update docs vis-a-vis ASK changes

* Cli: update transaction types to use new dynamic-signer methods

* CLI: Fix tests No. 1

what to do about write_keypair outstanding

* Work around `CliConfig`'s signer not necessarily being a `Keypair`

* CLI: Fix tests No. 2

* Remove unused arg

* Remove unused methods

* Move offline arg constants upstream

* Make cli signing fallible

Co-authored-by: Trent Nelson <trent.a.b.nelson@gmail.com>

sdk/src/signers.rs

@@ -48,6 +48,34 @@ impl Signers for [Box<dyn Signer>] {
     default_keypairs_impl!();
 }
 
+impl Signers for Vec<&dyn Signer> {
+    default_keypairs_impl!();
+}
+
+impl Signers for [&dyn Signer] {
+    default_keypairs_impl!();
+}
+
+impl Signers for [&dyn Signer; 0] {
+    default_keypairs_impl!();
+}
+
+impl Signers for [&dyn Signer; 1] {
+    default_keypairs_impl!();
+}
+
+impl Signers for [&dyn Signer; 2] {
+    default_keypairs_impl!();
+}
+
+impl Signers for [&dyn Signer; 3] {
+    default_keypairs_impl!();
+}
+
+impl Signers for [&dyn Signer; 4] {
+    default_keypairs_impl!();
+}
+
 impl<T: Signer> Signers for [&T; 0] {
     default_keypairs_impl!();
 }
@@ -111,4 +139,22 @@ mod tests {
             vec![Signature::default(), Signature::default()],
         );
     }
+
+    #[test]
+    fn test_dyn_keypairs_by_ref_compile() {
+        let foo = Foo {};
+        let bar = Bar {};
+        let xs: Vec<&dyn Signer> = vec![&foo, &bar];
+        assert_eq!(
+            xs.sign_message(b""),
+            vec![Signature::default(), Signature::default()],
+        );
+
+        // Same as above, but less compiler magic.
+        let xs_ref: &[&dyn Signer] = &xs;
+        assert_eq!(
+            Signers::sign_message(xs_ref, b""),
+            vec![Signature::default(), Signature::default()],
+        );
+    }
 }