modernize media capture to latest spec

What do we need to change in this plugin to adhere to https://w3c.github.io/mediacapture-main/ ?

Per CB-12841, we also have consensus around dropping the native UI portions of the plugin. What would that look like?

Worth noting that iOS 11 Mobile Safari has this built-in. Perhaps some testing there is in order to see what would need to be done / what kind of polyfill/shimming we should expect to put in place to gracefully transition over to the vendor-provided APIs.

This would definitely necessitate a major version bump.