gz service -r should not require --reqtype and --reptype

[azeey]

Desired behavior

gz service -r automatically determines the Request and Response message types. So instead of:

gz service -s /gazebo/worlds --reqtype gz.msgs.Empty --reptype gz.msgs.StringMsg_V -r 'unused: true' --timeout 2000

I'd like to run:

gz service -s /gazebo/worlds  -r 'unused: true' --timeout 2000

Alternatives considered

n/a

Implementation suggestion

gz service -i is able to retrieve the request and response types so it should be possible to use the same mechanism when making service calls via gz service -r.

Additional context

n/a