Separate lazy and eager

[MarcoGorelli]

No description provided.

[MarcoGorelli]

from the last consortium call:

• OK with not limiting to the Standard? If some implementation wants to add something not forbidden by the Standard, then they're free to do so (just like for Array API).
  Marco: any objections to not limiting to the standard?
  Ralf: seems to work fairly reasonable with the array API. So long as an array API implementation passes the test suite, then it is fine.
  Marco: okay, this should make things easier for writing an implementation.

this doesn't remove anything from the standard, it just adds some syntax and constructs which haven't yet been approved - safe to merge then