Include constexprs in cache keys, fixes #7322, reverts #7344 (#7348)

See #7332, this reinstates the change where constexprs are included in
kernel cache keys, but only includes constexprs, and doesn't include the
`id(var_dict)` which is nonpredictable. (from:
`self.used_global_vals[(node.id, id(var_dict))] = (copy.copy(val),
var_dict)`)

# New contributor declaration
- [x] I am not making a trivial change, such as fixing a typo in a
comment.

- [x] I have written a PR description following these
  [rules](https://cbea.ms/git-commit/#why-not-how).

- [x] I have run `pre-commit run --from-ref origin/main --to-ref HEAD`.

- Select one of the following.
  - [x] I have added tests.
    - `/test` for `lit` tests
    - `/unittest` for C++ tests
    - `/python/test` for end-to-end tests
  - [ ] This PR does not need a test because `FILL THIS IN`.

- Select one of the following.
  - [x] I have not added any `lit` tests.
- [ ] The `lit` tests I have added follow these [best
practices](https://mlir.llvm.org/getting_started/TestingGuide/#filecheck-best-practices),
including the "tests should be minimal" section. (Usually running Python
code
    and using the instructions it generates is not minimal.)

Author: leijurv

python/test/unit/runtime/test_cache.py

@@ -400,6 +400,25 @@ def kernel():
     assert not kernel.used_global_vals
 
 
+def test_constexpr_cache_invalidation_recreated(device):
+
+    def test_run(val):
+        VAL = tl.constexpr(val)
+
+        @triton.jit
+        def kernel(out):
+            tl.store(out, VAL)
+
+        out = torch.zeros(1, device=device)
+        kernel[(1, )](out)
+        return out.item()
+
+    assert test_run(123) == 123
+    assert test_run(123) == 123
+    assert test_run(1234) == 1234
+    assert test_run(1234) == 1234
+
+
 def test_jit_warmup_cache(device) -> None:
 
     @triton.jit

python/triton/runtime/jit.py

@@ -696,6 +696,12 @@ def cache_key(self):
             dependencies_finder.visit(self.parse())
             self.hash = dependencies_finder.ret + str(self.starting_line_number)
             self.used_global_vals = dict(sorted(dependencies_finder.used_global_vals.items()))
+
+            from triton.language.core import constexpr
+            self.hash += str([(name, val)
+                              for (name, _), (val, _) in self.used_global_vals.items()
+                              if isinstance(val, constexpr)])
+            self.hash = hashlib.sha256(self.hash.encode("utf-8")).hexdigest()
         return self.hash
 
     @property