feat(common/core): Add Activate Keyboard API call for common core processor

[rc-swag]

This affects the caps lock indicator when using Keyman for Windows but requires a change to the common core.

If Caps Lock is on and a new keyboard is selected that has a store(&CapsAlwaysOff) '1' system store the indicator will stay on. As soon as a key is pressed the Caps Lock Indicator will turn off and the correct output occurs. The reason windows can't easily turn off the Caps lock indicator when the keyboard is selected is because Caps store information is encapsulated in the common core processor.

Describe the solution you'd like

When selecting a new keyboard the Caps Indicator turn off at this time if the keyboard as a store settings store(&CapsAlwaysOff) '1'.

The code solution should be to add a API call to the core processor with a keyboardActivated type call. This can then return a action for the Caps Lock to be turned off. This api call could be extended to do any other "work" that needs to be done when a keyboard is selected.

It was considered to have a more specific ResetCapsLock call added to the API however the proposed solution is more extensible.