Fix pkg_resources deprecated

[hikeya]

Description

The pkg_resources package used by mqtt_connection_builder and others is scheduled to be removed as early as 2025-11-30.

Details

#626

Test Results

$ python -m unittest test.test_importlib_metadata -v
test_general_exception_handling_mqtt5_client_builder (test.test_importlib_metadata.TestImportlibMetadata.test_general_exception_handling_mqtt5_client_builder)
Test that general exceptions are handled correctly in mqtt5_client_builder ... ok
test_general_exception_handling_mqtt_connection_builder (test.test_importlib_metadata.TestImportlibMetadata.test_general_exception_handling_mqtt_connection_builder)
Test that general exceptions are handled correctly in mqtt_connection_builder ... ok
test_importlib_metadata_available (test.test_importlib_metadata.TestImportlibMetadata.test_importlib_metadata_available)
Test that importlib.metadata is available and working ... ok
test_importlib_metadata_import (test.test_importlib_metadata.TestImportlibMetadata.test_importlib_metadata_import)
Test that importlib.metadata is properly imported in the modified files ... ok
test_metrics_string_generation_mqtt5_client_builder (test.test_importlib_metadata.TestImportlibMetadata.test_metrics_string_generation_mqtt5_client_builder)
Test that mqtt5_client_builder uses importlib.metadata for version detection ... ok
test_metrics_string_generation_mqtt_connection_builder (test.test_importlib_metadata.TestImportlibMetadata.test_metrics_string_generation_mqtt_connection_builder)
Test that mqtt_connection_builder uses importlib.metadata for version detection ... ok
test_no_pkg_resources_import (test.test_importlib_metadata.TestImportlibMetadata.test_no_pkg_resources_import)
Test that pkg_resources is not imported in the modified files ... ok
test_package_not_found_handling_mqtt5_client_builder (test.test_importlib_metadata.TestImportlibMetadata.test_package_not_found_handling_mqtt5_client_builder)
Test that PackageNotFoundError is handled correctly in mqtt5_client_builder ... ok
test_package_not_found_handling_mqtt_connection_builder (test.test_importlib_metadata.TestImportlibMetadata.test_package_not_found_handling_mqtt_connection_builder)
Test that PackageNotFoundError is handled correctly in mqtt_connection_builder ... ok

----------------------------------------------------------------------
Ran 9 tests in 0.082s

OK

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.