feat(overlay): expose constants with overlay use (#15081)

# Description

`overlay use` now imports constants exported from modules, just like
`use`.

```nushell
# foo.nu
export const a = 1
export const b = 2
```

- `overlay use foo.nu` being equivalent to `use foo.nu *` and exposing
constants `$a = 1` and `$b = 2`
- `overlay use foo.nu -p` being equivalent to `use foo.nu` and exposing
the constant `$foo = {a: 1, b: 2}`

# User-Facing Changes

`overlay use` now imports constants just like `use`.

# Tests + Formatting

- 🟢 toolkit fmt
- 🟢 toolkit clippy
- 🟢 toolkit test
- 🟢 toolkit test stdlib

# After Submitting
N/A

crates/nu-parser/src/parse_keywords.rs

@@ -2977,8 +2977,7 @@ pub fn parse_overlay_new(working_set: &mut StateWorkingSet, call: Box<Call>) ->
     working_set.add_overlay(
         overlay_name.as_bytes().to_vec(),
         module_id,
-        vec![],
-        vec![],
+        ResolvedImportPattern::new(vec![], vec![], vec![], vec![]),
         false,
     );
 
@@ -3192,8 +3191,7 @@ pub fn parse_overlay_use(working_set: &mut StateWorkingSet, call: Box<Call>) ->
         working_set.add_overlay(
             final_overlay_name.as_bytes().to_vec(),
             origin_module_id,
-            definitions.decls,
-            definitions.modules,
+            definitions,
             has_prefix,
         );
     } else {