* 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)
Adds a new experimental `pulumi watch` CLI command which can be used for inner loop development on a Pulumi stack. This command is only available currently via `PULUMI_EXPERIMENTAL=true` while in active development.
The `watch` command does the following:
1. Watches the workspace (the tree rooted at the `Pulumi.yaml` file) for changes
2. Triggers an `update` to the stack whenever there is a change
3. Streams output containing summaries of key update events as well as logs from any resources under management into a combined CLI output
Part of https://github.com/pulumi/pulumi/issues/3448.
The PULUMI_EXPERIMENTAL flag also makes`query` and `policy` available.
The current pattern of using backend.Stack values in the CLI but
accepting backend.StackReference values in backend methods leads to
frequent transitions between these types. In the case of the HTTP
backend, the transition from a StackReference to a Stack requires an API
call. These changes refactor the backend.Backend API such that most of
its methods accept backend.Stack values in place of
backend.StackReference values, which avoids these transitions.
This removes two calls to the getStack API on the startup path of a
`pulumi preview`.
