Extension to dump and load domain state

[iboB]

dbg_dmp offers a way to dump the state of a domain in a human-readable format

an extension can be created which dumps the state into a machine-readable format (say json) and can then restore it

It can be useful for debugging, a minidump of sorts:

• Pointers must be turned into ids so pointers can be disambiguated but not bound to a run