Add PermissionDelegation feature (#5354)

This change implements the account permission delegation described in XLS-75d, see https://github.com/XRPLF/XRPL-Standards/pull/257.

* Introduces transaction-level and granular permissions that can be delegated to other accounts.
* Adds `DelegateSet` transaction to grant specified permissions to another account.
* Adds `ltDelegate` ledger object to maintain the permission list for delegating/delegated account pair.
* Adds an optional `Delegate` field in common fields, allowing a delegated account to send transactions on behalf of the delegating account within the granted permission scope. The `Account` field remains the delegating account; the `Delegate` field specifies the delegated account. The transaction is signed by the delegated account.

src/libxrpl/protocol/InnerObjectFormats.cpp

@@ -154,6 +154,10 @@ InnerObjectFormats::InnerObjectFormats()
             {sfIssuer, soeREQUIRED},
             {sfCredentialType, soeREQUIRED},
         });
+
+    add(sfPermission.jsonName.c_str(),
+        sfPermission.getCode(),
+        {{sfPermissionValue, soeREQUIRED}});
 }
 
 InnerObjectFormats const&