VAAPI Encoder 0.4.1

Fix a potential segmentation fault while enumerating devices.

• Lookup human readable render device names for easier selection.
• Use postproc element from the selected encoder device to avoid cross GPU transfers.
• Legacy encoder also uses legacy postproc. Makes device selection easier. Move to new encoders if issues pop up. (But no need to have new va plugin installed if only interested in legacy encoders )
• Some internal restructuring. Fingers crossed I didn't break anything by accident..

Fix some encoder strings names being garbage.

• Change encoder search approach. Should pick up encoders on multi-gpu setups.
• Encoder IDs have changed. You will have to reconfigure your encoder.
• Log only prints discovered encoders now. Logs current used encoder.

• Support for new VA plugins from GStreamer 1.22.
• Previous encoders are labeled "Legacy", but are still select-able.
• Support for low power encoder variants (by kode54).
• Support for AV1 encoder (AV1 is WIP by upstream, expected to hit in the next GStreamer cycle).
• Support for more input color formats.
• Much more informative logging all over the place.
• Probably other small fixes and hiccups.

Starting with this version the minimum required OBS version is now v28.

Note that the default install path has changed to the user's home directory. If you want a system wide install, use Meson's --prefix and --libdir options accordingly.