Che plugin broker should support ephemeral mode

[amisevsk]

Tracking for upstream eclipse-che/che#11554

Goal would be to at least implement a proof of concept / figure out if it's possible without significant reworking.

[ibuziuk]

@l0rd has some ideas how this could be implemented so we need to sync in order to decide what approach we would take ephemeral support

[l0rd]

The idea would be to leverage configmaps and environment variables to share metadata amongst containers instead of using a volume for it.

And delegating the download of .theia or tar.gz files to the plugins sidecars themselves instead of the having the broker do it.

[amisevsk]

PR: eclipse-che/che#11786

[garagatyi]

@amisevsk can we close this issue?

[amisevsk]

@garagatyi I think we should close it once 6.14 is on prod.