[MLIR] `scf-parallel-loop-fusion` misses fusion when one loop contains a private `memref.alloc`

`scf-parallel-loop-fusion` misses a fusion opportunity for two adjacent `scf.parallel` loops with identical bounds. The first loop only allocates a private temporary buffer inside each iteration and writes to it:
```bash
%alloc = memref.alloc() : memref<1xf32>
memref.store %cst, %alloc[%c0]
```
The second loop independently copies `%arg0[i]` to `%arg1[i]`. The inner `%alloc` is private to the first loop iteration and cannot alias `%arg0` or `%arg1`, so it should not block fusion of the two parallel loops. Currently, the loops remain separate, resulting in a missed optimization.

### Input Program
**input.mlir**
```llvm
module {
func.func @alloc_alias(%arg0: memref<16xf32>, %arg1: memref<16xf32>) {
%c0 = arith.constant 0 : index
%c1 = arith.constant 1 : index
%c16 = arith.constant 16 : index
%cst = arith.constant 0.000000e+00 : f32
scf.parallel (%arg2) = (%c0) to (%c16) step (%c1) {
%alloc = memref.alloc() : memref<1xf32>
memref.store %cst, %alloc[%c0] : memref<1xf32>
scf.reduce
}
scf.parallel (%arg2) = (%c0) to (%c16) step (%c1) {
%0 = memref.load %arg0[%arg2] : memref<16xf32>
memref.store %0, %arg1[%arg2] : memref<16xf32>
scf.reduce
}
return
}
}
```

### Command
```bash
mlir-opt input.mlir --scf-parallel-loop-fusion
```

Version: b37a8a70cc98915d157cac2f049e9f46d6da8fe5

Start by running the supplied input.mlir with mlir-opt --scf-parallel-loop-fusion and inspect the scf-parallel-loop-fusion implementation and its existing tests. Reproduce the missed fusion involving the private memref.alloc, then add coverage and verify that the two adjacent scf.parallel loops are fused without invalid aliasing assumptions.

Written by the indexing model from the issue text.