Bluetooth: ISO: Expose CIG_ID, CIS_ID, BIG_Handle and BIS_Number

Expose the IDs, handles and numbers of CIGs, BIGs, CISes and BISes
via the ISO info struct. This information may be needed by higher
layer (such as the Basic Audio Profile (BAP)) or used as indexes
for arrays in the application layer.

The location of the CIG_ID, CIS_ID, BIG_Handle and BIS_Number
are moved to the location struct inside of struct bt_conn_iso
instead of being stored directly in it.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>