* Centralize the retry package for the otlp exporters
* Add dependabot config
* Use unified internal/retry module in otlp exporters
* Remove otlpmetric and otlptrace internal/retry module
* Run go mod tidy in otlp{metric,trace}
* Use gRPC ClientConn for otlpmetricgrpc conn handling
* Update PR number
* Update otlpmetrichttp to use retry package
* Remove old commented code
* Add all other external changes to changelog
