Add a windows stage2 pipeline that runs on schedule and on demand (comment trigger)

[ViktorHofer]

Motivation: We want to make sure that the we can build the VMR with a just live-built VMR (called stage2 build) so that we can detect issues earlier, before we do a SDK toolset re-bootstrap.

Building windows stage1 and stage2 combined takes close to 4 hours which is too long to enable in PRs. We should add a pipeline that runs on schedule (i.e. once per day) and on demand (comment trigger) that has two jobs:

• win-x64
• win-x64 BuildPass="stage2"

The second job should depend on the previous job and build with the produced SDK and packages.