Previously, `loadLibs` was called inside the `optimize` function of
the media-optimization-worker, which meant that it could be hit
multiple times causing load errors (as seen in b69c2f7311)
This commit moves that call to a specific message handler (the `install` message)
for the service worker, and refactors the service for the media-optimization-worker
to wait for this installation to complete before continuing with processing
image optimizations.
This way, we know for sure based on promises and worker messages
that the worker is installed and has all required libraries
loaded before we continue on with attempting any processing. The
change made in b69c2f7311 is no
longer needed with this commit.
2461ed303c