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/util/check.cpp

@@ -21,7 +21,7 @@ std::string StrFormatInternalBug(std::string_view msg, std::string_view file, in
     return strprintf("Internal bug detected: %s\n%s:%d (%s)\n"
                      "%s %s\n"
                      "Please report this issue here: %s\n",
-                     msg, file, line, func, PACKAGE_NAME, FormatFullVersion(), PACKAGE_BUGREPORT);
+                     msg, file, line, func, CLIENT_NAME, FormatFullVersion(), CLIENT_BUGREPORT);
 }
 
 NonFatalCheckError::NonFatalCheckError(std::string_view msg, std::string_view file, int line, std::string_view func)