Add H265 support

[joaoantoniocardoso]

What to test:

• Create fakesrc h265 UDP and receive via GStreamer
• Create fakesrc h265 RTSP and receive via GStreamer
• Create fakesrc h265 UDP and receive via QGC
• Create fakesrc h265 RTSP and receive via QGC
• Create fakesrc h265 UDP or RTSP and receive via WebRTC¹
• Create USB camera h265 UDP or RTSP and receive via WebRTC¹
• Redirect from an IP camera h265 stream and receive via WebRTC¹
• Redirect from an IP camera h265 stream (RTSP) and receive via QGC

¹: It works on Safari 18, but for 17.6, the H265 feature flag needs to be enabled.

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To receive from UDP:

gst-launch-1.0 -vc \
    udpsrc address=127.0.0.1 port=5600 close-socket=false auto-multicast=true \
    ! application/x-rtp, payload=96 \
    ! rtph265depay \
    ! avdec_h265 std-compliance=normal \
    ! videoconvert \
    ! autovideosink sync=false

To receive from RTSP:

gst-launch-1.0 -vc \
    rtspsrc location=rtsp://0.0.0.0:8554/0 latency=0 \
    ! application/x-rtp, payload=96 \
    ! rtph265depay \
    ! avdec_h265 std-compliance=normal \
    ! videoconvert \
    ! autovideosink sync=false

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Useful to check if the system supports H265 decoding (which doesn't mean it supports it via WebRTC):

1. open video_demo_hevc
2. open chrome://media-internals

[patrickelectric]

Fix #256