Refactor SignerSource to expose DerivationPath to other kinds of signers (#16933)

* One use statement

* Add stdin uri scheme

* Convert parse_signer_source to return Result

* A-Z deps

* Convert Usb data to Locator

* Pull DerivationPath out of Locator

* Wrap SignerSource to share derivation_path

* Review comments

* Check Filepath existence, readability in parse_signer_source

clap-utils/src/memo.rs

@@ -1,5 +1,4 @@
-use crate::ArgConstant;
-use clap::Arg;
+use {crate::ArgConstant, clap::Arg};
 
 pub const MEMO_ARG: ArgConstant<'static> = ArgConstant {
     name: "memo",