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

programs/bpf/Cargo.lock

@@ -3461,6 +3461,7 @@ dependencies = [
  "num-derive 0.3.0",
  "num-traits",
  "pbkdf2 0.6.0",
+ "qstring",
  "rand 0.7.3",
  "rand_chacha 0.2.2",
  "rand_core 0.6.2",
@@ -3479,6 +3480,7 @@ dependencies = [
  "solana-program 1.7.0",
  "solana-sdk-macro 1.7.0",
  "thiserror",
+ "uriparse",
 ]
 
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