[Dashboard Controls] Create State Storage for Control Group

[ThomThomson]

The Control Group component will be in charge of its own state storage, Redux Toolkit should be used to store all of this state. Some state items which will need to be stored include:

• The embeddables for each child control
• The order of the children
• The layout options for the control group - Whether the controls flow horizontally, or vertically

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)