* feat: enhance WPgxTestSuite with dynamic app name and config

 - Renamed `container_test_example.go` to `use_testcontainers_test.go` for clarity.
 - Added logic to set `POSTGRES_APPNAME` environment variable to "WPgxTestSuite" if not already set, ensuring consistent application naming.
 - Updated `setupWithContainer` to use dynamic username and password from `suite.Config`, enhancing flexibility and security.
 - Improved test suite configuration by leveraging environment variables, allowing for more dynamic and adaptable test setups.

* fix: update GitHub Actions workflow to trigger only on main branch

Removed the additional branch patterns "feat/" and "fix/" from the GitHub Actions workflow configuration. This change ensures that the workflow is triggered only on pull requests targeting the "main" branch. By simplifying the branch
conditions, we streamline the CI process, reducing unnecessary runs and focusing on the primary development branch. This update aligns with our goal to maintain a more efficient and focused CI/CD pipeline.

* feat: enhance test suite with new test cases and container setup

 - Added `TestDumpState` to verify the `DumpState()` method functionality, ensuring data is correctly dumped and loaded.
 - Introduced `TestGetRawPool` and `TestGetPool` to validate pool retrieval methods.
 - Implemented `containerTestSuite` to test container-based setup paths, including `TestContainerSetup` and `TestContainerTeardown`.
 - Enhanced error handling tests with `TestEnsureDirErrorPath` and `TestTearDownTestErrorHandling` to ensure robustness in directory creation and container teardown.
 - Utilized environment variable `POSTGRES_APPNAME` for container test configuration.

* lint