#3414 [Benchmark] Fix startup crashes and Windows version detection

说明

Fix two crashes when running `BENCH.bat`:

- Define `port` before using it to start the server, preventing a `NameError`.
- Read `CMakeLists.txt` explicitly as UTF-8 with BOM support, preventing a `UnicodeDecodeError` on Windows systems using CP932.

Validation:
- All 17 existing benchmark tests passed.
- Checked default, configured, overridden, and occupied port paths with mocks.
- Checked UTF-8 and UTF-8 BOM files with a simulated CP932 default.