feat: allow Tensor.store API to receive .var as value

This patch allows Tensor.store API (which is connected to `nki.language.store`) to accept a more
generic `Core.Value` type.

The motivation is tracing of interop/test/examples/matmul.py, specifically the `nki_matmul_basic_` function.

After apply #111, tracing the Python function was raising the following error message:

```
error:
line 44:
  nl.store(result[i_out_p, i_out_f], value=result_sbuf)
  ^-- expecting tensor access
```

It is because its `value` keyword argument was having the following expression:
```
KLR.Trace.Term.expr (KLR.Core.Expr.value (KLR.Core.Value.var "5")) (KLR.Trace.TermType.obj `object)
```
which could not be converted to Access through the FromNKI typeclass.

The "5" temporary variable was emerging from the right hand side of the definition of `result_sbuf`:

```
result_sbuf = nl.copy(result_psum, dtype=result.dtype)
```

To convert the value of "5", it seems we need to get the generated trace and find assignment to "5"
because:

```
def RValue : Term -> Trace Term
...
  | .expr e@(.call ..) ty => do
       let v := (<- genName).toString
       add_stmt (.assign v e)
       return .expr (.value $ .var v) ty
```

the `add_stmt` is just adding a Core statement to `State.body`.

Skimming through `State.body` and finding this assignment to "5" didn't seem something we wanted to do inside Tensor.store,
so instead I slightly chose a conservative approach and simply removed the shape checker.

But any other reasonable option is still fine with me.

Author: aqjune-aws

KLR/Trace/Tensor.lean

@@ -51,12 +51,8 @@ nki load (src : Access) (dtype : Dtype := .float32) := do
   let dst <- declare "load" dtype shape .sbuf
   return .store (.simple dst) .load [.access src]
 
-nki store (dst : Access) (value : Access) := do
-  let s1 <- dst.shape
-  let s2 <- value.shape
-  if s1 != s2 then
-    throw s!"incompatible shapes {s1} {s2}"
-  return Term.store dst .save [.access value]
+nki store (dst : Access) (value : Core.Value) := do
+  return Term.store dst .save [value]
 
 nki tensor_scalar (data : Access)
                   (op0 : AluOp)