Bluetooth: Rework the HCI header set

In order to have clean, self-contained HCI headers that do not have any
dependencies towards the Host or any other part of the system (except
types), reorganize the headers in the following way:

- Split out the macros and structs from hci.h to a new hci_types.h
- Merge the existing hci_err.h into the new hci_types.h

Fixes #58214.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>