Che operator should propagate an env varialble START_OPENVSX to the plugin registry

[l0rd]

Is your enhancement related to a problem? Please describe

The plugin registry is going to embed an OpenVSX instance (including postgres) and can require up to 1.5GB.

But if the admin configures Che to use an external OpenVSX Registry (i.e. specifies pluginRegistry.openVSXURL in the CheCluster) Che is still starting the embedded OpenVSX instance.

The embedded OpenVSX Registry should not be started if the user has specified pluginRegistry.openVSXURL.

Describe the solution you'd like

• Che operator should propagate the START_OPENVSX env variable (through a ConfigMap) to the plugin registry container
• The env variable should be set to true if the user hasn't specified a pluginRegistry.openVSXURL, set to false otherwise.
• The Plugin registry should start the openVSX instance if START_OPENVSX is set to true and should not start if the env variable is set to false or doesn't exist.