Bluetooth: controller: Fix reconfiguring of CIG and CISes

Up until now, it has not been possible to reconfigure a CIG and its
CISes after initial configuration, without first removing the CIG.

With this commit, le_set_cig_parameters allows the following
reconfiguration operations in configuration state:
- Set new CIG configuration parameters on existing CIG
- Iteratively configure single CIS (of more CISes)
- Increment number of CISes via multiple configuration calls
- Keep handle- and CIS_ID relation

Changes:
- Pass handles in le_set_cig_parameters from ll_cig_parameters_commit
  via output variable.
- Implement CIG state variable instead of 'started', with states
  IDLE/CONFIGURABLE, ACTIVE and INACTIVE.
- Implement ll_conn_iso_stream_get_by_id for easier access to specific
  CIS.

This fixes the following CIS Central EBQ tests:
- HCI/CIS/BI-10-C
- HCI/CIS/BI-11-C
- HCI/CIS/BI-13-C
- HCI/CIS/BV-05-C

Signed-off-by: Morten Priess <mtpr@oticon.com>