[Feature]: VP9 encoding support for BMG and LNL

### What Feature?

Both BMG and LNL are recent platforms, and AFAIK both support VP9 hardware encoding. Is there any particular reason this support is missing?

I use my Arc Pro B50 in my homelab to transcode videos uploaded to Immich (a self‑hosted alternative to Google Photos). VP9 is the default codec to which all uploaded videos are transcoded to cover the majority of devices without AV1 and HEVC decoding support. Sure, I can use H.264 for that purpose, but those files are larger.

### What's the usage scenario would be benifited?

Transcode for media delivery

### What impacted?

At least Immich users, since VP9 is the default codec there. Also, many Jitsi Meet instances still use VP9 as the default codec instead of AV1 or H.264.

### Do you want to contribute a patch to develop this feature?

No.