Add CosmosDB components

[eerhardt]

See #359

[danmoseley]

from @mitchdenny :
Our plan is to try and take this PR into the repo for our preview 1 release. I think in terms of division of labour I would focus on the App Model side and Eric can hopefully work on the component side. Hopefully we can get close to done with you tomorrow but if not we’ll finish it off.

[eerhardt]

Closing. This has been merged into main with #359 and release/8.0-preview1 with #669. Separate issues have been opened to track remaining work in this component.