test: add comprehensive tests for provider and resources

- Add provider unit tests for all configuration scenarios
- Test provider with environment variables and config precedence
- Add metadata and configure tests for all resources
- Test that resources implement required interfaces
- Increase provider coverage from 0% to 93.9%
- Increase resources coverage from 1.8% to 8.8%
- Increase total coverage from 29.8% to 39.3%

Author: Trozz