With this change, tests can specify `self.extra_init = [{ipcbind: True}]` to
start a node listening on an IPC socket, instead of needing to choose which
node binary to invoke and what `self.extra_args=[["-ipcbind=..."]]` value to
pass to it.
The eliminates boilerplate code #30437 (interface_ipc_mining.py), #32297
(interface_ipc_cli.py), and #33201 (interface_ipc.py) previously needed in
their test setup.
3cc9a06c8d