[massis08]

Reasoning

This PR introduces end-to-end support for USB as a built-in NMOS transport. The implementation adds the required transport definitions, sender and receiver support, SDP parsing utilities, and redundancy handling to enable USB-based media workflows.

Explanation

USB transport support

• Add USB transport schemas as built-in transport definitions.
• Add support for USB senders and receivers.
• Extend nmos-cpp-node to expose and manage USB senders and receivers.
• Implement USB redundancy support.

SDP parsing

• Implement usb_sdp_utils for parsing USB SDP files.
• Make mediaclk optional when parsing USB SDP.
• Produce an empty ts-refclk when no clock information is present in the SDP.
• Read the a=privacy attribute from either the session level or the media level.

@LufeBisect

[pedro-alves-ferreira]

LGTM