normalize special characters in module names to allow variable access (#14353)

Fixes #14252

# User-Facing Changes

- Special characters in module names are replaced with underscores when
  importing constants, preventing "expected valid variable name":

```nushell
> module foo-bar { export const baz = 1 }
> use foo-bar
> $foo_bar.baz
```

- "expected valid variable name" errors now include a suggestion list:

```nushell
> module foo-bar { export const baz = 1 }
> use foo-bar
> $foo-bar
Error: nu::parser::parse_mismatch_with_did_you_mean

  × Parse mismatch during operation.
   ╭─[entry #1:1:1]
 1 │ $foo-bar;
   · ────┬───
   ·     ╰── expected valid variable name. Did you mean '$foo_bar'?
   ╰────
```

crates/nu-protocol/src/module.rs

@@ -167,7 +167,7 @@ impl Module {
                 vec![]
             } else {
                 vec![(
-                    final_name.clone(),
+                    normalize_module_name(&final_name),
                     Value::record(
                         const_rows
                             .into_iter()
@@ -425,3 +425,32 @@ impl Module {
         result
     }
 }
+
+/// normalize module names for exporting as record constant
+fn normalize_module_name(bytes: &[u8]) -> Vec<u8> {
+    bytes
+        .iter()
+        .map(|x| match is_identifier_byte(*x) {
+            true => *x,
+            false => b'_',
+        })
+        .collect()
+}
+
+fn is_identifier_byte(b: u8) -> bool {
+    b != b'.'
+        && b != b'['
+        && b != b'('
+        && b != b'{'
+        && b != b'+'
+        && b != b'-'
+        && b != b'*'
+        && b != b'^'
+        && b != b'/'
+        && b != b'='
+        && b != b'!'
+        && b != b'<'
+        && b != b'>'
+        && b != b'&'
+        && b != b'|'
+}