Improve type safety on Workflows and Activities

## Describe the feature

I'd like to explore an improvement to the .NET SDK that makes it easier to build out workflows and their activities in a way that ensures that the inputs and outputs align with expectations.

I can see two ways of going about this:
1) In the SDK, add an overload that supports generic typing. If developers wish to invoke workflows or activities created in a different language, they're welcome to do so using the method already provided, but this overload would provide the developer some piece of mind that if a refactoring changes the expected input or output type of a workflow or activity, that the issue will be caught at development/compile time instead of runtime when the object fails to map properly.

2) Offer a source generator that introduces a static method for each workflow and activity that's appropriately typed. For example, rather than having `context.CallActivityAsync(nameof(MyActivity), "test value");` a static extension method would be introduced that provides `static Task CallMyActivityAsync(string value, DaprActivityOptions? options = null);`

## Release Note
RELEASE NOTE: **ADD** Stronger type safety validation in workflows and workflow activities