Allow register a workflow using `String` instead of only class canonical name

[kaibocai]

Describe the proposal

When registering a workflow, we pass the workflow class and its canonical name is used to store the workflow. This is not clear when customers use HTTP requests to start the workflow.

For example: customers tend to use
POST http://localhost:3500/v1.0-beta1/workflows/dapr/DemoWorkflow/start to start a workflow, which is not correct. Instead, it should use the class canonical name in the URL
POST http://localhost:3500/v1.0-beta1/workflows/dapr/io.dapr.examples.workflows.DemoWorkflow/start

Java SDK should provide the flexibility to register a workflow by any name given by customers.

[kaibocai]

I can work on this

[kaibocai]

/assign

[salaboy]

@kaibocai any updates on this?