Revert "Simplify c10::string_view implementation (#108479)"
This reverts commit ce03b78a8f463139c87a4bf42e8f37ebabca5b0f.
Reverted https://github.com/pytorch/pytorch/pull/108479 on behalf of https://github.com/huydhn due to Sorry for reverting you change, it is failing internal builds ([comment](https://github.com/pytorch/pytorch/pull/108479#issuecomment-1707033082))
