This is a design of API that could be used to create BASE configuration manage
its broadcast (setup extended advertising, periodic advertising and
BASE advertisements, stop, resume, terminate and modify them)

This patch implements Broadcast feature in host. It includes
implementation of ISO in host, with application API, HCI commands and
ISO event handling. Host is now capable of managing BIGs with subgroups
and BISes, updating Broadcast announcements and pushing data to ISO, to
send in BIS events.

Maximum extended advertising size was set to 251 to fit Periodic
advertising data connected with Broadcast Audio
Announcement Service advertisements by default.

This patch does not implement Broadcast sink, only source.

This patch adds commands to btshell to allow creating BIGs, BIG
subgroups and BISe and create and manage Broadcast advertisements.

ble_gap_adv_get_free_instance browses through list of advertising
instances and returns first that is not yet configured. Previously,
user had to track which instance is used by themselves, and could only
check if advertising is active, via ble_gap_ext_adv_active

This is simplified wrapper for Broadcast, that allows to create
Broadcast advertisements with sane defaults for advertising parameters.
Application still needs to build BASE configuration to use it.

Added application that has stored LC3 coded audio in form of sine sweep
from 100Hz to 20kHz. Application creates Broadcast announcement, builds
BIG with 1 or 2 BISes and starts to broadcast sample data.

This sample uses Auracast package to broadcast audio