Specify the source address for outbound audio and video traffic

[cgutman]

Description

This PR implements proper source address preservation for video and audio traffic. Previously, outgoing traffic would be subject to regular OS routing logic, so it could be sent with a source address different than the address where incoming traffic from the host was received.

This work is also necessary to unblock IPv6 support in #571 due to IPv6 temporary addresses being preferred as source addresses for outbound traffic.

Tested:

• Windows (send_batch() and fallback send() path)
• Linux (send_batch() with UDP_SEGMENT, send_batch() without UDP_SEGMENT, and fallback send() path)
• macOS (send() only because send_batch() is unimplemented)

Screenshot

Issues Fixed or Closed

Fixes #1568

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Dependency update (updates to dependencies)
• Documentation update (changes to documentation)
• Repository update (changes to repository files, e.g. .github/...)

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated the in code docstring/documentation-blocks for new or existing methods/components

Branch Updates

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must be updated before it can be merged. You must also
Allow edits from maintainers.

• I want maintainers to keep my branch updated