Fix long calc times

[Aras14HD]

We had three 100% cpu spikes before, all were due to nested operations, with 9e99999999 at the base.

After some investigation, I found the root cause to be the cloning of the top exponent number every op.
After I changed that to move, the example I used to test went down to ~1s total time.

As that is still slow, I changed the integer construction limit to 10000000 (one order of magnitude less, switches to approximate earlier).

The latest hours long problem was due to the copying of that top exponent thousands of times. I limited the steps to 10 for now.

[Aras14HD]

If we want to have not much of a change (other than keeping the biggest step), we could set the limit to 30.

[tolik518]

As long as it doesn't use up all the memory I'm fine with it :D

Upper limit of memory shouldn't be more than 10GB though, as I run lots of other stuff on my machine.

I should introduce a memory limit in the docker-compose file I think

Edit: assign me if it's ready for review btw

[Aras14HD]

So an individual integer should be at most on the order of 10^10000000, which is <4MiB, that times 30 gives <119MiB, less than 1GiB. One could still write a comment full of individual factorials, which would be 909, 9 of which would be <4MiB, 90 of which would be <400KiB and 810 of which would be <40KiB, together gives <<105MiB.

Lowering the construction limit further (possible with config) would proportionally lower that RAM use as well.