[mlir][vector] Use `source` as the source argument name (#158258)
This patch updates the following ops to use `source` (instead of
`vector`) as the name for their source argument:
* `vector.extract`
* `vector.scalable.extract`
* `vector.extract_strided_slice`
This change ensures naming consistency with the "builders" for these Ops
that already use the name `source` rather than `vector`. It also
addresses part of:
* https://github.com/llvm/llvm-project/issues/131602
Specifically, it ensures that we use `source` and `dest` for read and
write operations, respectively (as opposed to `vector` and `dest`).