Add timeout/heartbeat feature

[AdrienChampion]

Would be great to add either a timeout option, or a "heartbeat" one (limit on the number of instructions executed, does not depend on the machine it's running on).

In case it helps, here's some wat making owi sym run for very long. It's Ackermann with m = 4.

Ackermann.wat

(module
  (import "symbolic" "i32_symbol" (func $gen_i32 (result i32)))

  (func $ack (param i32 i32) (result i32)
    block  ;; label = @1
      local.get 0
      i32.eqz
      br_if 0 (;@1;)
      loop  ;; label = @2
        block  ;; label = @3
          block  ;; label = @4
            local.get 1
            br_if 0 (;@4;)
            i32.const 1
            local.set 1
            br 1 (;@3;)
          end
          local.get 0
          local.get 1
          i32.const -1
          i32.add
          call $ack
          local.set 1
        end
        local.get 0
        i32.const -1
        i32.add
        local.tee 0
        br_if 0 (;@2;)
      end
    end
    local.get 1
    i32.const 1
    i32.add)
  (func $start
    (local $result i32)
    i32.const 4
    call $gen_i32
    call $ack
    local.set $result
    (if
        (i32.lt_s (i32.const 72) (local.get $result))
        (then unreachable)
    )
  )

  (start $start)
)

[zapashcanon]

I believe having both makes sense. We should add them to owi c, owi sym and owi run (I'm less sure about owi script). @epatrizio, is this something you would like to try implementing ? We already have a timeout mechanism for the fuzzer so it shouldn't be too hard to implement. The hearbeat one may be a little bit more tricky due to parallel execution in the symbolic case.

(also cc @Swrup who may be interested in implementing this :-))