Added vscode-insiders path installed via snap (#137117)

Closes  #137116

<b>Before</b>
VS Code Insiders installed via Snap isn't detected.

<b>After</b>
```sh
[✓] VS Code (version 1.84.0-insider)
    • VS Code at /snap/code-insiders/current/usr/share/code-insiders
    • Flutter extension version 3.75.20231002
```

packages/flutter_tools/lib/src/vscode/vscode.dart

@@ -240,6 +240,7 @@ class VsCode {
   //   /usr/share/code/bin/code
   //   /snap/code/current/usr/share/code
   //   /usr/share/code-insiders/bin/code-insiders
+  //   /snap/code-insiders/current/usr/share/code-insiders
   // Linux Extensions:
   //   $HOME/.vscode/extensions
   //   $HOME/.vscode-insiders/extensions
@@ -251,6 +252,10 @@ class VsCode {
         '/usr/share/code-insiders',
         '.vscode-insiders',
       ),
+      const VsCodeInstallLocation(
+        '/snap/code-insiders/current/usr/share/code-insiders',
+        '.vscode-insiders',
+      ),
     ], fileSystem, platform);
   }
 

packages/flutter_tools/test/general.shard/vscode/vscode_test.dart

@@ -46,11 +46,12 @@ void main() {
     final Platform platform = FakePlatform(environment: <String, String>{'HOME': home});
 
     fileSystem.directory(fileSystem.path.join('/snap/code/current/usr/share/code', '.vscode')).createSync(recursive: true);
+    fileSystem.directory(fileSystem.path.join('/snap/code-insiders/current/usr/share/code-insiders', '.vscode-insiders')).createSync(recursive: true);
 
     final FakeProcessManager processManager = FakeProcessManager.list(<FakeCommand>[]);
 
     final List<VsCode> installed = VsCode.allInstalled(fileSystem, platform, processManager);
-    expect(installed.length, 1);
+    expect(installed.length, 2);
   });
 
   testWithoutContext('can locate installations on macOS', () {