fast idiv (#9755)

* fast idiv with tests and fuzzer

* Add todo comment

* Add env variable to toggle fast_idiv

* Move env check

* Add fuzz fast_idiv to ci

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Co-authored-by: chenyu <chenyu@fastmail.com>

setup.py

@@ -13,6 +13,7 @@ testing_minimal = [
   "pytest",
   "pytest-xdist",
   "hypothesis",
+  "z3-solver"
 ]
 
 setup(name='tinygrad',