Enable HTTP/2.0 support for the SDK.

[lalitb]

1ds cpp sdk currently uses HTTP/1.1 to push events to the ingestion service. This issue is open to explore adding support for HTTP/2.0 in the library. HTTP/2.0 is in general more secure and performant as compared to HTTP/1.1.

1DS SDK uses different client libraries to add HTTP support depending on the platform it is built for. Had a quick validation on the HTTP/2.0 support for all the platforms

• Android - The default HTTP library part of Android SDK doesn't have HTTP/2.0
  support. This needs to be replaced with okHTTP to add support.
• Apple - HTTP/2.0 is supported from iOS9 onwards.
• WinINet - Fully supports HTTP/2.0
• libcurl - has an external dependency on Nghttp2 to add the support.

While there is no immediate plan to support this requirement, unless there is enough traction on this issue, and/or contributors are ready to add the support.

[lalitb]

None of the collector URLs configured in 1DS SDK have HTTP/2.0 enabled.

But this can be tested in Japan west : onedscolprdjpw02.japanwest.cloudapp.azure.com

[lalitb]

The support is added for:

Posix/curl: #1068
Android (allow adding different android http implementation) : #1067 ( enable plugging the okhttp3 package)
Windows and iOS is already supported by Native HTTP Libraries

Closing this issue. Will create a separate issue to add okhttp support as external module or addition package.