add -f, --force for save command (#7262)

# Description

Closes: #6920 

# User-Facing Changes

```
❯ "asdf" | save dump.rdb
Error:
  × Destination file already exists
   ╭─[entry #21:1:1]
 1 │ "asdf" | save dump.rdb
   ·               ────┬───
   ·                   ╰── Destination file '/tmp/dump.rdb' already exists
   ╰────
  help: you can use -f, --force to force overwriting the destination
```
# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

crates/nu-engine/src/eval.rs

@@ -910,7 +910,15 @@ pub fn eval_element_with_input(
                                 Argument::Positional(expr.clone()),
                                 Argument::Named((
                                     Spanned {
-                                        item: "--raw".into(),
+                                        item: "raw".into(),
+                                        span: *span,
+                                    },
+                                    None,
+                                    None,
+                                )),
+                                Argument::Named((
+                                    Spanned {
+                                        item: "force".into(),
                                         span: *span,
                                     },
                                     None,