distributed collectives (#1519)

* feat: world

* feat: tests

* feat: no more backwards

* feat: recv into

* feat: whoops

* feat: test in ci

* feat: some debug logging

* feat: workflow naming

* feat: need to set pythonpath

* feat: just send to same device

* feat: allreduce

* feat: test

* feat: need contiguous

* feat: test in ci

* feat: exit with correct code

* feat: don't need that

* feat: opencl wait_for just doesn't work

* feat: synchronize on out

* feat: try?

* feat: try again?

* feat: add extra realizes

* feat: print

* feat: seed

* feat: tol

* feat: test ones and zeros

* feat: remove print

* feat: are you just flaky

* feat: seperate scatter and gather?

* feat: just try synchronizing

* feat: remove print again

* feat: bring back difference

* feat: no sync

* feat: revert that

* feat: back to wait_for

* fix: typo

.github/workflows/test.yml

@@ -158,6 +158,7 @@ jobs:
         name: Test multigpu
         run: |
           PYTHONPATH="." python test/external/dist/test_world.py
+          PYTHONPATH="." python test/external/dist/test_collectives.py
 
   testmetalwebgpu:
     name: Metal and WebGPU Tests