Bluetooth: hci: Extend VS fatal error for hard hault and assert

Extend current implementation of vendor-specific HCI events related
with Zephyr Fatal Error. The extended event is able to carry Zephyr
system wide fatal error as well as Controller related assertion.
That gives a possibility to use the event by bt_ctlr_assert_handle
or k_sys_fatal_error_handler to send information about unrecoverable
failures over HCI interface.

There are added two types of errors to Zephyr Fatal Error event:
- system fault error like e.g. Hard Fault. This one caries reason of
  a fault and a stack frame in the data field. The stack frame is
  defined for Corte-M SoCs only.
- Controller assert. The data field caries file name and line of code
  where an assert happened.

Except that the extended event can be used by Host, it can serve as a
debug mean to conformance testing of the Controller.

Signed-off-by: Piotr Pryga <piotr.pryga@nordicsemi.no>