scripted-diff: Rename PACKAGE_* variables to CLIENT_*

This change ensures consistent use of the `CLIENT_` namespace everywhere
in the repository.

-BEGIN VERIFY SCRIPT-

ren() { sed -i "s/\<$1\>/$2/g" $( git grep -l "$1" ./cmake ./src :\(exclude\)./src/secp256k1 ./test ) ; }

ren PACKAGE_NAME      CLIENT_NAME
ren PACKAGE_VERSION   CLIENT_VERSION_STRING
ren PACKAGE_URL       CLIENT_URL
ren PACKAGE_BUGREPORT CLIENT_BUGREPORT

-END VERIFY SCRIPT-

test/functional/tool_wallet.py

@@ -203,7 +203,7 @@ class ToolWalletTest(BitcoinTestFramework):
         locked_dir = self.nodes[0].wallets_path
         error = 'Error initializing wallet database environment "{}"!'.format(locked_dir)
         if self.options.descriptors:
-            error = f"SQLiteDatabase: Unable to obtain an exclusive lock on the database, is it being used by another instance of {self.config['environment']['PACKAGE_NAME']}?"
+            error = f"SQLiteDatabase: Unable to obtain an exclusive lock on the database, is it being used by another instance of {self.config['environment']['CLIENT_NAME']}?"
         self.assert_raises_tool_error(
             error,
             '-wallet=' + self.default_wallet_name,