Setup failing mips program

[martyall]

Setup a failing MIPS test due to padding errors

I added 2 tests to o1vm/tests/test_mips_elf.

# one time make command to build bin files
> make build-mips-programs
> cd o1vm
> RUST_LOG=debug cargo test --release --test test_mips_elf -- --nocapture

1. test_nor_execution: This checks the correct execution of the nor.asm program.
2. test_nor_proving: This checks the prove/verify steps from the main loop. It is currently failing because padding with zeros is not a valid way to extend a proof to the full domain. NOTE: This test also builds an SRS from scratch, it will take a while. This cost is amortized the more tests we add.

Changes

1. Add a halt_address field to cannon::VmConfiguration type. This flag allows us to signal the step function that we are finished executing -- if the next instruction pointer is the halt_address, stop execution. This hack was borrowed from the cannon codebase.

2. Factor out the core logic from pickles/main.rs to pickles/mod.rs so that it can be exported via o1vm::pickles. I didn't change any of the logic, but in order to add the "pad an incomplete execution" logic I had to separate some things out.

3. Add a dummy ProofInputs::pad function that pads a proof with zeros. We know this isn't working, but I did this as a way to stub out where the correct solution can go.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 24 lines in your changes missing coverage. Please review.

Project coverage is 74.63%. Comparing base (343132b) to head (be3660f).
Report is 19 commits behind head on master.

Files with missing lines	Patch %	Lines
o1vm/src/pickles/main.rs	0.00%	13 Missing ⚠️
o1vm/src/interpreters/mips/witness.rs	0.00%	7 Missing ⚠️
o1vm/src/cli/cannon.rs	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2921      +/-   ##
==========================================
- Coverage   74.66%   74.63%   -0.03%     
==========================================
  Files         259      259              
  Lines       61713    61734      +21     
==========================================
+ Hits        46075    46078       +3     
- Misses      15638    15656      +18     

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