multimedia/ffmpeg: Add NETWORK DEFAULT OPTION

Details:
Disabling the NETWORK OPTION (DEFAULT) allows users to compile ffmpeg
without networking code in libavcodec.

PR: 268786
Reported by: Alexander Ushakov <alexander@polyvizor.com>
MFH: 2023Q1

(cherry picked from commit 8855990a698ea489ad155282471df4ce864b8fad)