Bluetooth: Audio: Make PACS notify bonded clients on reconnect

This fix allows PACS to notify bonded clients, that were disconnected
when a characteristic with notify property was changed, are being
reconnected.

This fix also implements a defer work so to not block the bt rx
thread during auth callbacks. All other notify calls are for
consistency and style also moved to use the defer work.

Signed-off-by: Fredrik Danebjer <frdn@demant.com>