- Create providers/common/ with sse_builder, message_converter, think_parser,
heuristic_tool_parser, error_mapping
- Update nvidia_nim/utils and errors to re-export from common for backward compat
- Update all provider clients and tests to import from providers.common
- Remove duplicated files from nvidia_nim/utils/
Co-authored-by: Ali Khokhar <alishahryar2@gmail.com>