Move `BorrowedBuf` and `BorrowedCursor` from `std:io` to `core::io` Tracking issue: https://github.com/rust-lang/rust/issues/117693 ACP: https://github.com/rust-lang/libs-team/issues/290
Move `BorrowedBuf` and `BorrowedCursor` from `std:io` to `core::io` Tracking issue: https://github.com/rust-lang/rust/issues/117693 ACP: https://github.com/rust-lang/libs-team/issues/290