Bluetooth: controller: Create HCI stubs for CIG/CIS creation and removal

Put infrastructure for the following HCI commands/events in place:
* LE Set CIG Parameters command
* LE Remove CIG command
* LE Create CIS command
* LE Accept CIS Request command
* LE Reject CIS Request command
* LE CIS Established event
* LE CIS Request event

Signed-off-by: Wolfgang Puffitsch <wopu@demant.com>