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-

src/rpc/server.cpp

@@ -154,12 +154,12 @@ static RPCHelpMan help()
 
 static RPCHelpMan stop()
 {
-    static const std::string RESULT{PACKAGE_NAME " stopping"};
+    static const std::string RESULT{CLIENT_NAME " stopping"};
     return RPCHelpMan{"stop",
     // Also accept the hidden 'wait' integer argument (milliseconds)
     // For instance, 'stop 1000' makes the call wait 1 second before returning
     // to the client (intended for testing)
-                "\nRequest a graceful shutdown of " PACKAGE_NAME ".",
+                "\nRequest a graceful shutdown of " CLIENT_NAME ".",
                 {
                     {"wait", RPCArg::Type::NUM, RPCArg::Optional::OMITTED, "how long to wait in ms", RPCArgOptions{.hidden=true}},
                 },