enh(io): use variant slot for parameters changed in grabbers

Description

Since SParameters uses a unique slot (variant-typed) for parameters changes, we can do the same on all Grabber services for both slot and signals.

Proposal

• create signals/ slots parameterChanged(parameters_t, std::string) in IGrabber
• replace every intChanged, boolChanged etc by the new one.
• replace also the forwards signals in SGrabberProxy

Functional specifications

• Behavior should remain the same, it will only reduce the number of slots / signals to a unique one.

Technical specifications

• We need to get the variant type used by SParameters by including #include <ui/base/parameter.hpp>
• A lot of xml configuration needs to be updated along with channels

Test plan

• Test applications that uses video (using SGrabberProxy and using a specific grabber)