Added support for vscode and vscode-insiders installed via Flatpak (#137123)

Closes #137122

<b>Before</b>
VS Code and VS Code Insiders installed via Flatpak aren't detected

<b>After</b>
```sh
[✓] VS Code (version 1.82.2)
    • VS Code at /var/lib/flatpak/app/com.visualstudio.code/x86_64/stable/active/files/extra/vscode
    • Flutter extension version 3.74.0

[✓] VS Code (version 1.84.0-insider)
    • VS Code at /var/lib/flatpak/app/com.visualstudio.code.insiders/x86_64/beta/active/files/extra/vscode-insiders
    • Flutter extension version 3.75.20231002
```

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

@@ -237,17 +237,30 @@ class VsCode {
   }
 
   // Linux:
+  //   Deb:
   //     /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
+  //   Snap:
+  //     /snap/code/current/usr/share/code
+  //   Flatpak:
+  //     /var/lib/flatpak/app/com.visualstudio.code/x86_64/stable/active/files/extra/vscode
+  //     /var/lib/flatpak/app/com.visualstudio.code.insiders/x86_64/beta/active/files/extra/vscode-insiders
   // Linux Extensions:
+  //   Deb:
   //     $HOME/.vscode/extensions
-  //   $HOME/.vscode-insiders/extensions
+  //   Snap:
+  //     $HOME/.vscode/extensions
+  //   Flatpak:
+  //     $HOME/.var/app/com.visualstudio.code/data/vscode/extensions
+  //     $HOME/.var/app/com.visualstudio.code.insiders/data/vscode-insiders/extensions
   static List<VsCode> _installedLinux(FileSystem fileSystem, Platform platform) {
     return _findInstalled(<VsCodeInstallLocation>[
       const VsCodeInstallLocation('/usr/share/code', '.vscode'),
       const VsCodeInstallLocation('/snap/code/current/usr/share/code', '.vscode'),
+      const VsCodeInstallLocation(
+        '/var/lib/flatpak/app/com.visualstudio.code/x86_64/stable/active/files/extra/vscode',
+        '.var/app/com.visualstudio.code/data/vscode',
+      ),
       const VsCodeInstallLocation(
         '/usr/share/code-insiders',
         '.vscode-insiders',
@@ -256,6 +269,10 @@ class VsCode {
         '/snap/code-insiders/current/usr/share/code-insiders',
         '.vscode-insiders',
       ),
+      const VsCodeInstallLocation(
+        '/var/lib/flatpak/app/com.visualstudio.code.insiders/x86_64/beta/active/files/extra/vscode-insiders',
+        '.var/app/com.visualstudio.code.insiders/data/vscode-insiders',
+      ),
     ], fileSystem, platform);
   }
 

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

@@ -54,6 +54,27 @@ void main() {
     expect(installed.length, 2);
   });
 
+  testWithoutContext('can locate VS Code installed via Flatpak', () {
+    final FileSystem fileSystem = MemoryFileSystem.test();
+    const String home = '/home/me';
+    final Platform platform = FakePlatform(environment: <String, String>{'HOME': home});
+
+    fileSystem.directory(fileSystem.path.join(
+      '/var/lib/flatpak/app/com.visualstudio.code/x86_64/stable/active/files/extra/vscode',
+      '.var/app/com.visualstudio.code/data/vscode',
+    )).createSync(recursive: true);
+
+    fileSystem.directory(fileSystem.path.join(
+      '/var/lib/flatpak/app/com.visualstudio.code.insiders/x86_64/beta/active/files/extra/vscode-insiders',
+      '.var/app/com.visualstudio.code.insiders/data/vscode-insiders',
+    )).createSync(recursive: true);
+
+    final FakeProcessManager processManager = FakeProcessManager.list(<FakeCommand>[]);
+
+    final List<VsCode> installed = VsCode.allInstalled(fileSystem, platform, processManager);
+    expect(installed.length, 2);
+  });
+
   testWithoutContext('can locate installations on macOS', () {
     final FileSystem fileSystem = MemoryFileSystem.test();
     const String home = '/home/me';