Object Transfer Service Client made "official"

[Thalley]

We want an upstream Object Transfer Service client, so that the le-audio Media Control Sercvice Client can use that one instead of the le-audio OTS client implementation.

The temporary OTC implementation in the le-audio stack could be a starting point, together with the already existing upstream OTS server.

2020.12.02, updated 2021-11-09

Todo:

• Take the implementation we have in the le-audio stack and check if it is sufficient and then move it to the same location as the OTS.
• We do have an impl, working, used for 1 1/2 a year--
• some ramp up required, read up etc.
• reshape as required for upstream
• style changes as per server implementation
• reviewed and merged
  • review comments regarding structures etc. would be expected
• Discussions around where to place, where and how the API will be
  • This task involves API definition--
    • Same or different APIs for OTS and OTC
  • API, code structure and so on as for other GATT clients
• Get ongoing OTS PR merged first?
• Also includes switching the media control to use the updated version

2021.03.10:

• Try to split this into smaller stories

2021.06.23:

• Reduce the stories down to 5, more APIs are upstream now making this task less than 8 stories