Removed the loadedalldata event

[heff]

Want to get this out before 5.0. Reasoning from #1676.

I think we need to deprecate the loadedalldata event for 5.0. It's a made up event (not from the video element) that has less use these days for a few reasons:

• For most cases, you should use the canplaythrough event instead of loadedalldata.
• Browsers manage their buffer more carefully now, they don't just load the whole video at once
• It doesn't apply to live events

[gkatsev]

Should we deprecate the other vjs-only events as well? Like firstplay?

[heff]

I think I tried that once and got push back because it's actually useful. Don't we use it in ads or somewhere externally?

[mmcc]

lgtm