fuse self-contained subgraphs

[Qazalin]

• Detect self-contained subgraphs
• Delete forced_realize

[geohot]

Can you comment this better? I think it might help while thinking about it too.

[Qazalin]

status: making progress on completing the logic for _can_localize

# is r + rest is a self-contained DAG within the large graph?
def _can_localize(r:LazyBuffer, *rest:LazyBuffer) -> bool

I plan to finish the spec and benchmark new fusion end-to-end.

[github-actions]

Changes

Name                           Lines    Diff    Tokens/Line    Diff
---------------------------  -------  ------  -------------  ------
tinygrad/engine/schedule.py      244     +17           14.0    -0.2


total lines changes: +17