Per [XLS-0095](https://xls.xrpl.org/xls/XLS-0095-rename-rippled-to-xrpld.html), we are taking steps to rename ripple(d) to xrpl(d).
This change modifies the binary name from `rippled` to `xrpld`, and creates a symlink named `rippled` that points to the `xrpld` binary.
Note that https://github.com/XRPLF/rippled/pull/5975 renamed any references to `rippled` in the CMake files and their contents, but explicitly maintained the `rippled` binary name by adding an exception. This change now undoes this exception and adds an explicit symlink instead.
