refactor: Make ToxAV independent of toxcore internals.

[iphydf]

closes #1431

This change is 

[codecov]

Codecov Report

Attention: Patch coverage is 58.86364% with 181 lines in your changes missing coverage. Please review.

Project coverage is 73.04%. Comparing base (102a1fa) to head (5f97890).
Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
toxav/msi.c	55.40%	66 Missing ⚠️
toxav/rtp.c	57.25%	53 Missing ⚠️
toxav/toxav.c	71.90%	34 Missing ⚠️
toxav/bwcontroller.c	15.15%	28 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2651      +/-   ##
==========================================
- Coverage   73.08%   73.04%   -0.04%     
==========================================
  Files         149      149              
  Lines       30531    30478      -53     
==========================================
- Hits        22313    22263      -50     
+ Misses       8218     8215       -3     

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[iphydf]

This is ready for review.

[Green-Sky]

toxav_old.c uses the Messenger logger, instead the ToxAV logger.

edit: I see that they are still more tightly coupled to messenger and conferences. Maybe we just remove them for v0.3 ?

[zoff99]

@Green-Sky "m_lossy_rtp_packet_cb" is actually a leftover that should be deleted. same as "RTP_Packet_Handler"

[Green-Sky]

@Green-Sky "m_lossy_rtp_packet_cb" is actually a leftover that should be deleted. same as "RTP_Packet_Handler"

True, fixed.

[zoff99]

@Green-Sky mergeable is failing because of the commit messages missing "refactor" or similar

[Green-Sky]

@Green-Sky mergeable is failing because of the commit messages missing "refactor" or similar

Yes, that is going to go away when I squash this pr.

[iphydf]

Reviewed 12 of 26 files at r1, 3 of 4 files at r2, 3 of 5 files at r3, 8 of 8 files at r4, all commit messages.
Reviewable status: 0 of 1 approvals obtained (waiting on @goldroom and @Green-Sky)

[Green-Sky]

Reviewed 12 of 26 files at r1, 3 of 4 files at r2, 3 of 5 files at r3, 8 of 8 files at r4, all commit messages.
Reviewable status: 0 of 1 approvals obtained (waiting on @goldroom)