Implement session state tracking for "Run and Debug" button when Inte…

[Prashant Kumar Rai (8prashant)]

Fixes #13001

When C_Cpp.intelliSenseEngine is set to "disabled", the language server client is not started. Previously, cpptools.buildAndDebug.isSourceFile and cpptools.buildAndDebug.isFolderOpen context keys (which control the visibility of the "Run / Debug C/C++ File" and "Add Debug Configuration" editor action buttons) were only updated within the language server client (client.ts). Consequently, disabling IntelliSense would cause the Run/Debug shortcut buttons to never appear in the editor title bar.

This PR updates the Debugger extension initialization (Debugger/extension.ts) to track active text editor changes and keep buildAndDebugIsSourceFile and buildAndDebugIsFolderOpen up to date regardless of whether IntelliSense is enabled or disabled.

Changes

1. Added updateBuildAndDebugSessionState and registered an onDidChangeActiveTextEditor listener in DebuggerExtension.initialize.
2. Added unit tests in Extension/test/scenarios/SingleRootProject/tests/buildAndDebug.test.ts verifying session state updates for source files, header files, non-C/C++ files, and undefined editors.

Verification

• Compiled with TypeScript (yarn compile) with 0 errors.
• Ran tests via yarn test --scenario=SingleRootProject and verified all BuildAndDebug SessionState Tests pass.