samples: Bluetooth: Add tx support for unicast audio server
samples: Bluetooth: Add tx support for unicast audio server

Add support to send mock data on any source endpoint/streams
configured by the client.

Signed-off-by: Emil Gydesen <a20314356615223738233ab4c4eb1cd8cd4146fa@nordicsemi.no>

galak/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr