All `add*Listener` and `add*Output` methods are
deprecated in favor of `addListener`.
As for the class themselves `VideoListener` and
`AudioListener` are not used internaly by ExoPlayer,
`VideoRendererEventListener`
and `AudioRendererEventListener` are use in their
place.
As a result `VideoListener` and `AudioListener`
can be deprecated in favor `Listener`.
On the other hand `TextOutput` and `MedataOutput`
are used both in the player interface and internally in
renderers.
This means that those class can't be deprecated.
There usage in the public interface are indirectly
deprecated as their is no way to use them without
using the deprecated `add*Output`.
Thus it's not an issue that the class themselves are
not deprecated.
#minor-release
PiperOrigin-RevId: 371318268
Also consolidate the threading warning info with the same info on the
hello world page and update the version that the
setThrowsWhenUsingWrongThread() method will be removed in.
PiperOrigin-RevId: 369657759
