knative - protected parameters - protecting action parameters with final annotation

OpenWhisk web actions has the ability to protect action parameters against accidental or intentional mutation in query or body parameters. Using the `final` annotation on an action seals all action parameters with predefined values and makes those parameters immutable. For example, to seal the name parameter:

```
$ wsk action update /guest/demo/hello \
--param name Jane \
--annotation final true \
--annotation web-export true
```

The result of these changes is that name is bound to Jane and may not be overridden by query or body parameters because of the final annotation. Any attempt to override a final parameter will result in a 400 Bad Request response.

Add this capability in knative web actions.