decorator: Replace ViewFuncT with ParamSpec.
decorator: Replace ViewFuncT with ParamSpec.

`ParamSpec` can be easily applied to many use cases of ViewFuncT with
`Concatenate` to help us get rid of the `cast` calls. This does not
include decorators that require the second argument being
`UserProfile`.

Signed-off-by: Zixuan James Li <74923aee05c23ca90566381b5d6b0cd9451b6054@gmail.com>

andersk/zulip,rht/zulip,andersk/zulip,zulip/zulip,zulip/zulip,andersk/zulip,zulip/zulip,zulip/zulip,rht/zulip,andersk/zulip,rht/zulip,rht/zulip,zulip/zulip,andersk/zulip,zulip/zulip,rht/zulip,andersk/zulip,rht/zulip,rht/zulip,zulip/zulip,andersk/zulip