Making open case-insensitive to file extensions (#10451)

# Description

Closes #10441 

Uses `String::to_lowercase()` when the file's extension `ext` is parsed
to allow `from_decl(format!("from {ext}"))` to return the desired output
regardless of extension case.

It doesn't work with sqlite files since those are handled earlier in the
parsing but I think is good- since there's no standard file extension
used by sqlite so a user will likely want case sensitivity in that case.

This also has the (possibly undesired) effect of making `open`
completely case insensitive, e.g. `open foo.JSON` will work on a file
named `foo.json` and vice versa. This is good on Windows as it treats
`foo.json` and `foo.JSON` as the same file, but may not be the desired
behaviour on Unix.

If this behaviour is undesired I assume it would be fixed with a
`#[cfg(not(unix))]` attribute on the `to_lowercase()` operation but that
produces slightly "uglier" code that I didn't wish to submit unless
necessary. 

old behaviour:

![image](https://github.com/nushell/nushell/assets/79598494/261df577-e377-44ac-bef3-f6384bceaeb5)

new behaviour: 

![image](https://github.com/nushell/nushell/assets/79598494/04271740-a46f-4613-a3a6-1e220ef7f829)


# User-Facing Changes

`open` will now present a table when `open`-ing files with captitalized
extensions rather than the file's raw data

# Tests + Formatting

new test: `parses_file_with_uppercase_extension` which tests the desired
behaviour

---------

Co-authored-by: Stefan Holderbach <sholderbach@users.noreply.github.com>

crates/nu-command/src/filesystem/open.rs

@@ -171,12 +171,11 @@ impl Command for Open {
                         metadata: None,
                         trim_end_newline: false,
                     };
-
                     let ext = if raw {
                         None
                     } else {
                         path.extension()
-                            .map(|name| name.to_string_lossy().to_string())
+                            .map(|name| name.to_string_lossy().to_string().to_lowercase())
                     };
 
                     if let Some(ext) = ext {

crates/nu-command/tests/commands/open.rs

@@ -1,8 +1,39 @@
 use nu_test_support::fs::Stub::EmptyFile;
+use nu_test_support::fs::Stub::FileWithContent;
 use nu_test_support::fs::Stub::FileWithContentToBeTrimmed;
 use nu_test_support::playground::Playground;
 use nu_test_support::{nu, pipeline};
 
+#[test]
+fn parses_file_with_uppercase_extension() {
+    Playground::setup("open_test_uppercase_extension", |dirs, sandbox| {
+        sandbox.with_files(vec![FileWithContent(
+            "nu.zion.JSON",
+            r#"{
+                "glossary": {
+                    "GlossDiv": {
+                        "GlossList": {
+                            "GlossEntry": {
+                                "ID": "SGML"
+                            }
+                        }
+                    }
+                }
+            }"#,
+        )]);
+
+        let actual = nu!(
+            cwd: dirs.test(), pipeline(
+            r#"
+                open nu.zion.JSON
+                | get glossary.GlossDiv.GlossList.GlossEntry.ID
+            "#
+        ));
+
+        assert_eq!(actual.out, "SGML");
+    })
+}
+
 #[test]
 fn parses_csv() {
     Playground::setup("open_test_1", |dirs, sandbox| {