Description of problem:
qemu-kvm has supported copy/paste in the vnc console since qemu-kvm 6.2.0, see: Bug 1874926 - [RFE] copy/paste support in qemu VNC console

Beside Libvirt, virt-viewer should also support this feature.

Steps to Reproduce:
1.Start VM with VNC has copy/paste enabled, use virt-viewer connect to VM vnc port
2.Try to copy some characters from client machine and paste them to VM
3.Try to copy some characters from VM and paste them to client machine

Actual results:
copy/paste in step 2 and 3 doesn't work

Expected results:
copy/paste works good

Additional info:
I have checked virt-viewer-11.0-1.el9.x86_64 and copy/paste doesn't work. As a reference, vncviewer provided by tigervnc-1.11.0-21.el9.x86_64 has copy/paste works