Rename EventEmitter to EventLogger

[jack-berg]

Our EventEmitter class is currently out of alignment with the spec, which calls the interface EventLogger instead. I attempted algin the naming with the spec in #4961, but punted after receiving pushback from the java SIG.

There was a recent attempt to rename EventLogger to EventEmitter in the spec, and after a long debate which included the spec SIG in addition to the event SIG, folks ultimately agreed on EventLogger.

The time is right for opentelemetry-java to align naming with the spec and rename EventEmitter to EventLogger. As discussed here, we should try to do this before the next release to bundle several breaking changes to the event API.