Adds a new test for invalid `tensor.unpack` operations where the output
rank does not match the expected rank (input rank + num inner tile
sizes). For example:
```mlir
tensor.unpack %output
inner_dims_pos = [0, 1]
inner_tiles = [32, 16]
into %input : tensor<64x32x16xf32> -> tensor<256x128xf32>
```
In addition, updates the corresponding error message to make it more
informative:
BEFORE:
```mlir
error: packed rank must equal unpacked rank + tiling factors}
```
AFTER:
```mlir
error: packed rank != (unpacked rank + num tiling factors), got 3 != 4
```
b27d97bef7