[test] create unit-test framework for RPC wallets (#2396)

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Co-authored-by: dni ⚡ <office@dnilabs.com>

flake.nix

@@ -40,6 +40,9 @@
             pytest-md = prev.pytest-md.overridePythonAttrs (
               old: { buildInputs = (old.buildInputs or []) ++ [ prev.setuptools ]; }
             );
+            types-mock = prev.pytest-md.overridePythonAttrs (
+              old: { buildInputs = (old.buildInputs or []) ++ [ prev.setuptools ]; }
+            );
           });
         };
       });