adjust memory of plug-in registry container based on CheCluster settings

[benoitf]

Is your enhancement related to a problem? Please describe

Today, OpenVSX could be run as part of the plug-in registry

But it consumes more memory than just the http service
So it would be nice if we want to use open-vsx.org and do not start OpenVSX in plug-in registry that we keep the low memoryLimit

Describe the solution you'd like

sets memory Request/Limit on plug-in registry based on the CheCluster openVSXURL flag

OpenVSXUrl:

• user-defined value: low memory : 256Mi limit
• empty : 2Gi and request to 500Mi

Discussion thread:
eclipse-che/che-plugin-registry#1324 (comment)

Based on that I would recommend a more robust memory setup done by che-operator:

if pluginRegistry.openVSXURL is NOT set we should set plugin registry memory:
limit to 2Gi
request to 500Mi
otherwise set the old (and less demanding) memory settings

Describe alternatives you've considered

Do not start plug-in registry at all (for example if editor is not CheTheia)

Additional context

No response