Evaluate removing curl dependency for Apple platform - Adding support for CFNetwork API

[lalitb]

Apple comes with CFNetwork API to enable applications to interact with FTP and HTTP protocols to access Internet resources. This means it doesn't explicitly need to use curl as an HTTP client library.

otel-cpp is designed to plugin any external client library by extending abstract classes defined in the ext::http::client namespace.
And HttpClientFactory factory is responsible to pick up the correct library based on the platform it is running.

CURL implementation is available here: https://github.com/open-telemetry/opentelemetry-cpp/tree/main/ext/include/opentelemetry/ext/http/client/curl
Similar implementation needs to be provided to support CFNetwork API.

This issue is created to evaluate whether CFNetwork can be supported, and probably raise another issue for the implementation.

[github-actions]

This issue was marked as stale due to lack of activity. It will be closed in 7 days if no furthur activity occurs.