let find take linebreaks into account in Value::String (#7789)

# Description

Fixes #7774. The functionality should be the same as feeding all
`PipelineDate::Value(Value::String(_,_),_)` into `lines` before putting
it into `find`.

# 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-command/tests/commands/find.rs

@@ -109,3 +109,15 @@ fn find_with_filepath_search_with_multiple_patterns() {
         assert_eq!(actual.out, r#"["amigos.txt","arepas.clu"]"#);
     })
 }
+
+#[test]
+fn find_takes_into_account_linebreaks_in_string() {
+    let actual = nu!(
+    cwd: ".", pipeline(
+    r#"
+        "atest\nanothertest\nnohit\n" | find a | length
+        "#
+    ));
+
+    assert_eq!(actual.out, "2");
+}