Remove curl dependency for Windows platform - Adding support for WinINet API

[lalitb]

Windows comes with WinINet 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 WinINet API.

[github-actions]

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