New candidate JEP: 335: Deprecate the Nashorn JavaScript Engine

[Jesus Luzon]

We use Nashorn heavily in our Edge at Riot for what we call our
transformation layer, where users wanting to expose their applications can
tranforms request and/or responses by writing JS snippets. Losing Nashorn
without any viable replacement would destroy much of the work we've done in
the past year and a half to make our Ecosystem highly configurable, so an
at the very least actual ETA on deprecation and an expected replacement
path would be ideal.