Bluetooth: Audio: Rename BASS and BASS client

Rename BASS to BAP Scan Delegator and BASS Client
to BAP Broadcast Assistant. This is the first step towards
integrating the BASS with the rest of BAP.

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

doc/connectivity/bluetooth/api/shell/bap_broadcast_assistant.rst

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+Bluetooth: Broadcast Audio Profile Broadcast Assistant
+######################################################
+
+This document describes how to run the BAP Broadcast Assistant functionality.
+Note that in the examples below, some lines of debug have been
+removed to make this shorter and provide a better overview.
+
+The Broadcast Assistant is responsible for offloading scan for a resource
+restricted device, such that scanning does not drain the battery. The Broadcast
+Assistant shall support scanning for periodic advertisements and may optionally
+support the periodic advertisements synchronization transfer (PAST) protocol.
+
+The Broadcast Assistant will typically be phones or laptops.
+The Broadcast Assistant scans for periodic advertisements and transfer
+information to the server.
+
+It is necessary to have :code:`BT_DEBUG_BAP_BROADCAST_ASSISTANT` enabled for
+using the Broadcast Assistant interactively.
+
+When the Bluetooth stack has been initialized (:code:`bt init`),
+and a device has been connected, the Broadcast Assistant can discover BASS on
+the connected device calling :code:`bap_broadcast_assistant discover`, which
+will start a discovery for the BASS UUIDs and store the handles, and
+subscribe to all notifications.
+
+.. code-block:: console
+
+   bap_broadcast_assistant - Bluetooth BAP Broadcast Assistant shell commands
+   Subcommands:
+      discover        :Discover BASS on the server
+      scan_start      :Start scanning for broadcasters
+      scan_stop       :Stop scanning for BISs
+      add_src         :Add a source <address: XX:XX:XX:XX:XX:XX> <type:
+                       public/random> <adv_sid> <sync_pa> <broadcast_id>
+                       [<pa_interval>] [<sync_bis>] [<metadata>]
+      mod_src         :Set sync <src_id> <sync_pa> [<pa_interval>] [<sync_bis>]
+                       [<metadata>]
+      broadcast_code  :Send a space separated broadcast code of up to 16 bytes
+                       <src_id> [broadcast code]
+      rem_src         :Remove a source <src_id>
+      read_state      :Remove a source <index>
+
+Example usage
+*************
+
+Setup
+=====
+
+.. code-block:: console
+
+   uart:~$ bt init
+   uart:~$ bt connect xx:xx:xx:xx:xx:xx public
+
+When connected
+==============
+
+Start scanning for periodic advertisements for a server:
+
+.. note::
+   The Broadcast Assistant will not actually start scanning for periodic
+   advertisements, as that feature is still, at the time of writing, not
+   implemented.
+
+.. code-block:: console
+
+   uart:~$ bap_broadcast_assistant discover
+   <dbg> bt_bap_broadcast_assistant.char_discover_func: Found 1 BASS receive states
+   <dbg> bt_bap_broadcast_assistant.read_recv_state_cb: src_id 0, PA 0, BIS 0, encrypt 0, addr 00:00:00:00:00:00 (public), sid 0, metadata_len 0
+   uart:~$ bap_broadcast_assistant scan_start
+   <dbg> bt_bap_broadcast_assistant.write_func: err: 0x00, handle 0x001e
+
+Adding a source to the receive state:
+
+.. code-block:: console
+
+   uart:~$ bap_broadcast_assistant add_src 11:22:33:44:55:66 public 5 1 1
+   BASS recv state: src_id 0, addr 11:22:33:44:55:66 (public), sid 5, sync_state 1, encrypt_state 000000000000000000000000000000000
+        [0]: BIS sync 0, metadata_len 0