Another round of edit to the specification

- Update description regarding control of number of elements to be
processed based on discussion threads and edit suggestions of Nick.
- Update descriptions of pseudo intrinsics vsetvl and vsetvlmax
- Update sub-topics to control of vector programming model to more
understanding phrases instead of the name of those CSRs.
- Use `argument` universally when describing intrinsics argments
instead of `operand` or `parameter`.
- Use `intrinsics` universally instead of `RVV C intrinsics` or
`intrinsics API`.
- Refind wordings mode.
- Fix grammatical errors across the whole specification based on
suggestions by ChatGPT.

Signed-off-by: eop Chen <[email protected]>