cheri_interrupt_state should be cheriot

[davidchisnall]

This attribute is specific to CHERIoT and very unlikely to exist on bigger systems. It is painful to implement on out-of-order cores.

We should keep the old name available as an alias, but issue a deprecated warning when it's used.

[resistor]

Relatedly, should we support some of the other attributes in the cheriot namespace as well? cheriot_compartment, for example? It's easy enough to have a second spelling.

[davidchisnall]

Yes, I think that’s a good idea. The calling convention-related ones, in particular, are a good idea. We can always have a macro that expands to one of a selection based on target if some other CHERI platforms have them.