.NET: CosmosDB Actor State Storage (#262)
* Implement CosmosDB actor state storage.
* Fix.
* Minor fixes.
* Fixes.
* Make CosmosDB initialization be lazy.
* Remove unnecessary read from write path.
* Throw on empty writes.
* Add arg validation for read.
* Add CosmosIdSanitizer.
* Fix.
* Fix.
* Simplify doc IDs.
* Update comment.
* fb
* Make LazyCosmosContainer internal and add tests.
* Make test constants public and remove IVT.
* Use source generated JSON context for future nativeAOT support.
* Re-add dropped comments.