Unit tests for LLMediaDataClient

This required a bit of refactoring of LLMediaDataClient:
- Created LLMediaDataClientObject ABC, which now has a
  concrete impl in LLVOVolume
- Created unit test with 6 tests (for now), testing
  - LLObjectMediaDataClient::fetchMedia()
  - LLObjectMediaDataClient::updateMedia()
  - LLObjectMediaNavigateClient::navigate()
  - queue ordering
  - retries
  - nav bounce back
- Also ensures that ref counting works properly (this is important, because
  ownership is tricky with smart pointers put into queues, peeled off
  into timers that fire and auto destruct, and HTTP responders that also
  auto-destruct)
- Had to fix LLCurl::Responder's stub, which was not initializing
  the ref count to 0, causing the ref counting tests to fail
  (boy, that was hard to find!).

Reviewed by Callum

0 files changed, 0 insertions, 0 deletions