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/signature.rs

@@ -139,6 +139,18 @@ pub trait Signer {
     fn try_sign_message(&self, message: &[u8]) -> Result<Signature, SignerError>;
 }
 
+impl PartialEq for dyn Signer {
+    fn eq(&self, other: &dyn Signer) -> bool {
+        self.pubkey() == other.pubkey()
+    }
+}
+
+impl std::fmt::Debug for dyn Signer {
+    fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
+        write!(fmt, "Signer: {:?}", self.pubkey())
+    }
+}
+
 impl Signer for Keypair {
     /// Return the public key for the given keypair
     fn pubkey(&self) -> Pubkey {
@@ -167,6 +179,15 @@ where
     }
 }
 
+impl<T> From<T> for Box<dyn Signer>
+where
+    T: Signer + 'static,
+{
+    fn from(keypair_util: T) -> Self {
+        Box::new(keypair_util)
+    }
+}
+
 #[derive(Debug, Error, PartialEq)]
 pub enum SignerError {
     #[error("keypair-pubkey mismatch")]
@@ -202,15 +223,14 @@ pub enum SignerError {
     UserCancel,
 }
 
-#[derive(Debug, Default)]
+#[derive(Clone, Debug, Default)]
 pub struct Presigner {
     pubkey: Pubkey,
     signature: Signature,
 }
 
 impl Presigner {
-    #[allow(dead_code)]
-    fn new(pubkey: &Pubkey, signature: &Signature) -> Self {
+    pub fn new(pubkey: &Pubkey, signature: &Signature) -> Self {
         Self {
             pubkey: *pubkey,
             signature: *signature,