* guix/jupyter/proxy.scm: New file.
* Makefile.am (SOURCES): Add it.
* guix-jupyter-container.scm (%main-kernel, %main-kernel-id)
(register-kernel, kernel-by-name): Remove.
(local-eval): No longer return COUNTER.
(general-handler): Rewrite to expect a <proxy-state> and to pass a
<proxy-state> to all the message type handlers.
(ignore-request, reply-execute-request, shutdown): Adjust accordingly.
<top level>: Create a <proxy-state> and pass it to 'server-kernels'.
* guix-jupyter-kernel.scm (%main-kernel, %main-kernel-id)
(register-proxy, proxy-by-name): Remove.
(general-handler): Rewrite to expect a <proxy-state> and to pass a
<proxy-state> to all the message type handlers.
(ignore-request, reply-execute-request, shutdown): Adjust accordingly.
(kill-containers): Remove.
<top level>: Create a <proxy-state> and pass it to 'server-kernels'.