Treat edge-cases on the VideoPlayer and MiniVideoRecorder

[rafaellehmkuhl]

• Assert video is available before start recording
• Auto-assign stream (only if there's only one stream available)
• Let the user know if the selected stream is loading or not available

Fix #773
Fix #270
Fix #763
Fix #764

[rafaellehmkuhl]

Converting to draft to change the default behavior when there's more than one stream available on a cold boot.

Good to go.

[joaoantoniocardoso]

Auto-assign stream (only if there's only one stream available)

I was thinking... This will create an inconvenient scenario where Cockpit changes all secondary video widgets to the same video if the older secondary streams are not available for some reason ( for example, if the guy is recreating or changing the endpoints configuration ).

[rafaellehmkuhl]

I was thinking... This will create an inconvenient scenario where Cockpit changes all secondary video widgets to the same video if the older secondary streams are not available for some reason ( for example, if the guy is recreating or changing the endpoints configuration ).

Actually, it will only do the auto-assign if there's no stream selected, so we are good.