Various performance optimizations

[DanBmh]

Reduced the image grabbing/processing time by about 30% for my a2A1920-160umBAS.
Instead of 18ms per frame it now only takes 12ms per frame.

Influence of changes:

• drop camera reconnecting and just fail (-1ms)
• ignore encoding changes on runtime (-0.25ms)
• default disabled status/params publishers (-4ms)
• optimized bit shift and chunking at grab (-0.5ms and -0.5ms)

The main reason for the time improvements is that the api calls in those code snippets take a lot of time.
There should be further optimization options in other methods as well. Basically the best option might be a complete reimplementation of the parameter handling which stores/updates them as class attributes each time they are changed, so that they don't need to be requested every time.

[FrancoisPicardDTI]

Hello @DanBmh
Thank you for your contributions! I can understand why you did that but what annoys me is that with your version, it is not possible for the user to change the chunk mode and the encoding at runtime, and it does not allow to reconnect the camera anymore if it is disconnected. I was not the philosophy followed when the driver has been developed in the first place. I need to think about how to make it more flexible, maybe through services. I am keeping the PR opened for now.