[mlir][linalg][nfc] Rename test files for linalg.{un}pack
Following on from #123902, removes "tensor" from test file names for
`linalg.pack` and `linalg.unpack` (which prior to #123902 were Tensor
dialect Ops).
To minimize PR noise, I am submitting this without a review. However,
please ping me if you believe this or similar changes should be reviewed
before merging.
