Emit error message when interpreter reaches max no. of steps

[ngernest]

See #91 (an attempt to resolve this is in #93):

How can I get the diagnostic to print out the MaxStepsReached error without the error being tied to a file?

In #93, when we do:

$ cargo run --package protocols-interp -- --verilog protocols/tests/adders/adder_d1/add_d1.v \
        --protocol protocols/tests/adders/adder_d1/add_d1.prot \
        -t protocols/tests/adders/adder_d1/both_threads_pass.tx \
        --max-steps 1

we get:

Error
Error

thread 'main' panicked at protocols/src/setup.rs:76:5:
Expected Ok, got Err(MaxStepsReached(1))
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

but ideally we'd like this to emit an error message