[x] Pyronia initialization (SI comm + memdom init) hook
[x] Allocate sensitive state (interpreter state, frames, Pyronia security context) in a separate memdom hook
[x] Initialize callstack callback with callstack generator (see #10)
[ ] Add interpreter_dom access adjustment hooks
[x] Callstack generator from Python callstack: Given a pointer to a current stack frame, create a callstack node for the current frame, and repeat until the main module frame (with no parent) is reached. Return the root of the callstack back to the caller.
Addresses #4 and #10
interpreter_domaccess adjustment hooks