AVM: high-level vm CIRCUIT spec, especially with I/O

[dbanks12]

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1. public-vm(circuit spec): internal call stack #4041
   A-documentation C-avm +2
   
2. public-vm(circuit spec): nested contract calls
3. public-vm(circuit spec): memory controller / user memory #4043
   A-documentation C-avm +2
   
4. public-vm(circuit spec): calldata
5. public-vm(circuit spec): storage controller
6. public-vm(circuit spec): messages, notehashes, nullifiers, blockheader
7. public-vm(circuit spec): chiplets - pull in high-level description from Zac's doc
8. public-vm(circuit spec): tables of all sub-operations #4042
   +0
9. public-vm(circuit spec): refresh architecture diagram