Update RTD to use Generic API v2 webhook

Update RTD to use Generic API v2 webhook

The old tokenless generic trigger url has been deprecated. Update
to using the new v2 API that requires a token.

This is a backwards incompatible change and modifies 2 things:

  * rtd-project is now the rtd-build-url parameter
  * rtd-token is a new required parameter

Issue: RELENG-879
Change-Id: I786240ab14cf95a2896d92d1c87aef9d7815d964
Co-Authored-By: Thanh Ha <thanh.ha@linuxfoundation.org>
Signed-off-by: Jeremy Phelps <jphelps@linuxfoundation.org>
Signed-off-by: Thanh Ha <thanh.ha@linuxfoundation.org>