[flang] Enforce a limit on recursive PDT instantiations

For pernicious test cases with explicit non-constant actual
type parameter expressions in components, e.g.:

  type :: t(k)
    integer, kind :: k
    type(t(k+1)), pointer :: p
  end type

we should detect the infinite recursion and complain rather
than looping until the stack overflows.

Differential Revision: https://reviews.llvm.org/D100065