Redesign console input and output using xtermjs

**Shared Program**: https://code.world/haskell#PpcrjDqEzZaVUG0a4_0b_Kg

**Description**

If a console program prints a lot of output, it gets very slow. The reason seems to be that instead of just appending the content to the existing output element, the entire last output element is rebuilt from scratch. This looks to be part of the collapsible UI code that was built for error reporting, but inexplicably includes output as well.

We should special-case normal output from programs, so that it is appended directly without rebuilding the element. If we could remove the collapsible UI at the same time, that's even better!