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-command/src/deprecated/source.rs

@@ -1,4 +1,4 @@
-use nu_engine::{eval_block, CallExt};
+use nu_engine::{eval_block_with_early_return, CallExt};
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{Category, Example, PipelineData, ShellError, Signature, SyntaxShape, Type};
@@ -48,7 +48,7 @@ impl Command for Source {
         let block_id: i64 = call.req_parser_info(engine_state, stack, 0)?;
 
         let block = engine_state.get_block(block_id as usize).clone();
-        eval_block(
+        eval_block_with_early_return(
             engine_state,
             stack,
             &block,

crates/nu-command/src/env/source_env.rs

@@ -1,6 +1,6 @@
 use std::path::PathBuf;
 
-use nu_engine::{eval_block, find_in_dirs_env, redirect_env, CallExt};
+use nu_engine::{eval_block_with_early_return, find_in_dirs_env, redirect_env, CallExt};
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
@@ -62,7 +62,7 @@ impl Command for SourceEnv {
         let block = engine_state.get_block(block_id as usize).clone();
         let mut callee_stack = caller_stack.gather_captures(&block.captures);
 
-        let result = eval_block(
+        let result = eval_block_with_early_return(
             engine_state,
             &mut callee_stack,
             &block,