ensure that when nu evaluates files, it allows early returns (#7415)

# Description

Fixes #7301.

# User-Facing Changes

`return` can now be used in scripts without explicit `def main`.

# Tests + Formatting

Don't forget to add tests that cover your changes. (I'm not sure how to
test this.)

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-cli/src/config_files.rs

@@ -41,6 +41,7 @@ pub fn read_plugin_file(
                 &contents,
                 &plugin_filename,
                 PipelineData::empty(),
+                false,
             );
         }
     }
@@ -93,6 +94,7 @@ pub fn eval_config_contents(
                 &contents,
                 &config_filename,
                 PipelineData::empty(),
+                false,
             );
 
             // Merge the environment in case env vars changed in the config