le_audio: Initial implementation of TMAP

Patch implements part of TMAP for discovering and parsing data from
server.

Tag: #feature
Test: atest le_audio_client_test
Sponsor: jpawlowski@
Bug: 150670922
Bug: 208972148
Change-Id: I3655237be2c19ae397fc20e4c0c48c906121deac
(cherry picked from commit 29f0859e167a0d3241920573982033d1551484f4)