move greptimeai.collector.__init__.py to greptimeai.collector.py
split otel from collector
GreptimeCallbackHandler does not inherit from Collector.
do not put langchain or openai in resource, for it can not be set multiple times in OTel. So langchain or openai will be set as column in metrics tables, and field in span_attributes in trace table
what's included
greptimeai.collector.__init__.pytogreptimeai.collector.pyotelfromcollectorGreptimeCallbackHandlerdoes not inherit fromCollector.