* Make `async:true` the default for `invoke` calls (#3750)
* Switch away from native grpc impl. (#3728)
* Remove usage of the 'deasync' library from @pulumi/pulumi. (#3752)
* Only retry as long as we get unavailable back. Anything else continues. (#3769)
* Handle all errors for now. (#3781)
* Do not assume --yes was present when using pulumi in non-interactive mode (#3793)
* Upgrade all paths for sdk and pkg to v2
* Backport C# invoke classes and other recent gen changes (#4288)
Adjust C# generation
* Replace IDeployment with a sealed class (#4318)
Replace IDeployment with a sealed class
* .NET: default to args subtype rather than Args.Empty (#4320)
* Adding system namespace for Dotnet code gen
This is required for using Obsolute attributes for deprecations
```
Iam/InstanceProfile.cs(142,10): error CS0246: The type or namespace name 'ObsoleteAttribute' could not be found (are you missing a using directive or an assembly reference?) [/Users/stack72/code/go/src/github.com/pulumi/pulumi-aws/sdk/dotnet/Pulumi.Aws.csproj]
Iam/InstanceProfile.cs(142,10): error CS0246: The type or namespace name 'Obsolete' could not be found (are you missing a using directive or an assembly reference?) [/Users/stack72/code/go/src/github.com/pulumi/pulumi-aws/sdk/dotnet/Pulumi.Aws.csproj]
```
* Fix the nullability of config type properties in C# codegen (#4379)
Replace the Source-based implementation of refresh with a phase that
runs as the first part of plan execution and rewrites the snapshot in-memory.
In order to fit neatly within the existing framework for resource operations,
these changes introduce a new kind of step, RefreshStep, to represent
refreshes. RefreshSteps operate similar to ReadSteps but do not imply that
the resource being read is not managed by Pulumi.
In addition to the refresh reimplementation, these changes incorporate those
from #1394 to run refresh in the integration test framework.
Fixes#1598.
Fixespulumi/pulumi-terraform#165.
Contributes to #1449.
* Protobuf changes to record dependencies for read resources
* Add a number of tests for read resources, especially around replacement
* Place read resources in the snapshot with "external" bit set
Fixespulumi/pulumi#1521. This commit introduces two new step ops: Read
and ReadReplacement. The engine generates Read and ReadReplacement steps
when servicing ReadResource RPC calls from the language host.
* Fix an omission of OpReadReplace from the step list
* Rebase against master
* Transition to use V2 Resources by default
* Add a semantic "relinquish" operation to the engine
If the engine observes that a resource is read and also that the
resource exists in the snapshot as a non-external resource, it will not
delete the resource if the IDs of the old and new resources match.
* Typo fix
* CR: add missing comments, DeserializeDeployment -> DeserializeDeploymentV2, ID check
