- Bumps the package version to 2.2.3 in `pyproject.toml` and `src/gmssl/_version.py`.
- Refactors all code examples in `README.md` to use explicit imports instead of wildcard imports.
- Improves the readability and clarity of the code examples by adding comments, assertions, and f-strings.
- Removes lengthy and unnecessary certificate and command-line output from the `README.md` to improve readability.

This commit implements an elegant, hybrid API for `Sm4Gcm` to provide a simple, thread-safe interface for common use cases while retaining the powerful streaming API for advanced scenarios.

- **New One-Shot API**:
  - Added two new class methods, `Sm4Gcm.encrypt()` and `Sm4Gcm.decrypt()`.
  - These methods are stateless and inherently thread-safe, as they encapsulate the entire `init -> update -> finish` lifecycle within a single call.

- **New Tests**:
  - Added functional tests for the new one-shot API, including a critical test for authentication failure (tampered ciphertext).
  - Added a new concurrent test case to `test_thread_safety.py` that specifically verifies the thread safety of the new class methods.

- **Updated Documentation**:
  - The `Sm4Gcm` docstring and the main `README.md` have been updated to explain the two API modes: the recommended, thread-safe one-shot methods, and the advanced, non-thread-safe streaming API which requires external locking.

- **Linting**:
  - Fixed all `ruff` linting errors that were introduced during development.