pts-bot: Fix GATT bindings to pass pts tests without LE audio profiles

Patch gatt proto specification and server implementation
with missing definitions and update the test service
with additional characteristics and descriptors.

 - Add the possibility of defining descriptors for
   GATT characteristics
 - Add missing bits for GATT permissions and properties

Bug: 279669844
Test: atest pts-bot:GATT/SR
Change-Id: Id8fae1f1f17000e2270961ade5fdf6f42bb679d6