Account for `no_init` flag

[tim-hoffman]

--no_init             Removes initializations to 0 of variables ("var") in the witness
                      generation code

The LLZK backend for circom needs to check this flag and use nondet instead of 0 initialization for vars.

[tim-hoffman]

Actually, we need to determine if this flag affects how the circom AST is formed or not. If it does, then the LLZK code generation may account for this flag automatically and no further work is needed.

[tim-hoffman]

Ran target/debug/circom --no_init --llzk -o target circom/tests/arrays/array_size_mismatch_store_0.circom and observed that the output has changed to simply initialize a nondet array instead of zero filling. That means it must be reflected in the AST.

• Add a unit test that runs with --non_init flag