util.standardize_path: properly handle "~" (user's home directory)

notably this is needed when the shell itself does not get a chance to expand "~",
e.g. when a path is passed via JSON-RPC

>>> os.path.normcase(os.path.realpath(os.path.abspath("~/.electrum/testnet/wallets/delete_me2")))
'/home/user/wspace/electrum/~/.electrum/testnet/wallets/delete_me2'
>>> os.path.normcase(os.path.realpath(os.path.abspath(os.path.expanduser("~/.electrum/testnet/wallets/delete_me2"))))
'/home/user/.electrum/testnet/wallets/delete_me2'

electrum/util.py

@@ -458,7 +458,12 @@ def assert_file_in_datadir_available(path, config_path):
 
 
 def standardize_path(path):
-    return os.path.normcase(os.path.realpath(os.path.abspath(path)))
+    return os.path.normcase(
+            os.path.realpath(
+                os.path.abspath(
+                    os.path.expanduser(
+                        path
+    ))))
 
 
 def get_new_wallet_name(wallet_folder: str) -> str: