Recursively export constants from modules (#10049)

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# Description
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https://github.com/nushell/nushell/pull/9773 introduced constants to
modules and allowed to export them, but only within one level. This PR:
* allows recursive exporting of constants from all submodules
* fixes submodule imports in a list import pattern
* makes sure exported constants are actual constants

Should unblock https://github.com/nushell/nushell/pull/9678

### Example:
```nushell
module spam {
    export module eggs {
        export module bacon {
            export const viking = 'eats'
        }
    }
}

use spam 
print $spam.eggs.bacon.viking  # prints 'eats'

use spam [eggs]
print $eggs.bacon.viking  # prints 'eats'

use spam eggs bacon viking
print $viking  # prints 'eats'
```

### Limitation 1:

Considering the above `spam` module, attempting to get `eggs bacon` from
`spam` module doesn't work directly:
```nushell
use spam [ eggs bacon ]  # attempts to load `eggs`, then `bacon`
use spam [ "eggs bacon" ]  # obviously wrong name for a constant, but doesn't work also for commands
```

Workaround (for example):
```nushell
use spam eggs
use eggs [ bacon ]

print $bacon.viking  # prints 'eats'
```

I'm thinking I'll just leave it in, as you can easily work around this.
It is also a limitation of the import pattern in general, not just
constants.

### Limitation 2:

`overlay use` successfully imports the constants, but `overlay hide`
does not hide them, even though it seems to hide normal variables
successfully. This needs more investigation.

# User-Facing Changes
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Allows recursive constant exports from submodules.

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crates/nu-cmd-lang/src/core_commands/overlay/use_.rs

@@ -68,7 +68,7 @@ impl Command for OverlayUse {
 
         let maybe_origin_module_id =
             if let Some(overlay_expr) = call.get_parser_info("overlay_expr") {
-                if let Expr::Overlay(module_id) = overlay_expr.expr {
+                if let Expr::Overlay(module_id) = &overlay_expr.expr {
                     module_id
                 } else {
                     return Err(ShellError::NushellFailedSpanned {
@@ -106,11 +106,11 @@ impl Command for OverlayUse {
         };
 
         if let Some(module_id) = maybe_origin_module_id {
-            // Add environment variables only if:
+            // Add environment variables only if (determined by parser):
             // a) adding a new overlay
             // b) refreshing an active overlay (the origin module changed)
 
-            let module = engine_state.get_module(module_id);
+            let module = engine_state.get_module(*module_id);
 
             // Evaluate the export-env block (if any) and keep its environment
             if let Some(block_id) = module.env_block {
@@ -122,7 +122,7 @@ impl Command for OverlayUse {
                 )?;
 
                 let block = engine_state.get_block(block_id);
-                let mut callee_stack = caller_stack.gather_captures(&block.captures);
+                let mut callee_stack = caller_stack.gather_captures(engine_state, &block.captures);
 
                 if let Some(path) = &maybe_path {
                     // Set the currently evaluated directory, if the argument is a valid path