Refactor remote-wallet path parsing (backport #16798) (#16894)

* SDK: More conversions for `Pubkey`

(cherry picked from commit 9b7120bf73)

* SDK: More conversion for `DerivationPath`

(cherry picked from commit 722de942ca)

* remote-wallet: Add helpers for locating remote wallets

(cherry picked from commit 64fcb792c2)

* remote-wallet: Plumb `Locator` into `RemoteWalletInfo`

(cherry picked from commit 3d12be29ec)

* remote-wallet: `derivation-path` crate doesn't like empty trailing child indexes

(cherry picked from commit 4ce4f04c58)

* remote-wallet: Move `Locator` to its own module

(cherry picked from commit cac666d035)

Co-authored-by: Trent Nelson <trent@solana.com>

sdk/program/src/pubkey.rs

@@ -1,7 +1,11 @@
 use crate::{decode_error::DecodeError, hash::hashv};
 use borsh::{BorshDeserialize, BorshSchema, BorshSerialize};
 use num_derive::{FromPrimitive, ToPrimitive};
-use std::{convert::TryFrom, fmt, mem, str::FromStr};
+use std::{
+    convert::{Infallible, TryFrom},
+    fmt, mem,
+    str::FromStr,
+};
 use thiserror::Error;
 
 /// Number of bytes in a pubkey
@@ -63,7 +67,16 @@ pub enum ParsePubkeyError {
     WrongSize,
     #[error("Invalid Base58 string")]
     Invalid,
+    #[error("Infallible")]
+    Infallible,
 }
+
+impl From<Infallible> for ParsePubkeyError {
+    fn from(_: Infallible) -> Self {
+        Self::Infallible
+    }
+}
+
 impl<T> DecodeError<T> for ParsePubkeyError {
     fn type_of() -> &'static str {
         "ParsePubkeyError"
@@ -88,6 +101,13 @@ impl FromStr for Pubkey {
     }
 }
 
+impl TryFrom<&str> for Pubkey {
+    type Error = ParsePubkeyError;
+    fn try_from(s: &str) -> Result<Self, Self::Error> {
+        Pubkey::from_str(s)
+    }
+}
+
 impl Pubkey {
     pub fn new(pubkey_vec: &[u8]) -> Self {
         Self(