Add version command with comprehensive unit tests and build integration

- Implement llama version command with table and JSON output formats
- Add build-time git information capture via scripts/generate_build_info.py
- Include comprehensive unit test suite (test_version.py, test_version_simple.py, test_version_integration.py)
- Add build system integration with custom setup.py command
- Update .gitignore to exclude generated build info file

Features:
- Display Llama Stack and client versions
- Show Python version and build information (git commit, date, branch, tag)
- Optional component/provider listing organized by API
- Support for both table and JSON output formats
- Build-time capture of git metadata for version tracking

Testing:
- 8 unit tests covering all functionality
- Integration tests for CLI execution
- Simple dependency-free validation tests
- Documentation for test suite and build process

Signed-off-by: Akram Ben Aissi <akram.benaissi@gmail.com>

llama_stack/cli/stack/list_providers.py

@@ -28,10 +28,11 @@ class StackListProviders(Subcommand):
         return [api.value for api in providable_apis()]
 
     def _add_arguments(self):
+        choices = self.providable_apis
         self.parser.add_argument(
             "api",
             type=str,
-            choices=self.providable_apis,
+            choices=choices if choices else None,
             nargs="?",
             help="API to list providers for. List all if not specified.",
         )