Remove deprecated `Process`

[plafer]

As discussed multiple times offline, we should remove the now deprecated Process in favor of the FastProcessor and build_trace() infrastructure.

As mentioned in #2400 (comment), we should also remember to remove the OverflowTable history.

[Farukest]

Hi @plafer @bobbinth

I've explored the codebase and understand the scope
I see it touches 85+ files but I'm happy to take this on. Could you assign it to me?

[plafer]

Hey @Farukest, this is a pretty critical one, so we'll take care of it.