[Pickers]: add loader for the time of processing request to selection of a large number of values

## Now
User can click on multiple checkboxes without waiting for requests to be processed. This may result in incorrect picker behaviour.

https://github.com/epam/UUI/assets/57751283/05987f5e-8ca3-43fe-ac4a-b563219663ca

## To Do
If the user has already clicked on checkbox, don't give him the possibility to click on another one until the previous request is processed

## Describe the solution you'd like