Limit impact of O(n^2) type analysis by imposing limit

Limit impact of O(n^2) type analysis by imposing limit

* module/language/cps/types.scm (infer-types): Add #:max-label-count
  argument.

* module/language/cps/type-fold.scm (compute-folded, fold-constants*):
  Disable for big functions.  Perhaps we can relax this if we find an
  O(n log n) way to represent types.