Che Theia can't reach Che plugin registry behind the proxy with TLS support

[dmytro-ndp]

Describe the bug

Plugins view is empty behind the proxy in CRW 2.1.0.RC3 based on Eclipse Che 7.9.2 with TLS support:

Theia image: quay.io/crw/theia-rhel8:2.1-23

Proxy settings:

  CHE_WORKSPACE_HTTPS__PROXY: 'http://10.0.148.146:3128'
  CHE_WORKSPACE_HTTP__PROXY: 'http://10.0.148.146:3128'

Downstream issue.

Che version

• latest
• nightly
• other: CRW 2.1.0.RC3 based on Eclipse Che 7.9.2

Steps to reproduce

1. Start workspace
2. Open Plugins View

Runtime

• kubernetes (include output of kubectl version)
• Openshift (include output of oc version)
• minikube (include output of minikube version and kubectl version)
• minishift (include output of minishift version and oc version)
• docker-desktop + K8S (include output of docker version and kubectl version)
• other: OCP 3.11

Installation method

• crwctl
• che-operator
• minishift-addon
• I don't know

Environment

• my computer
  • Windows
  • Linux
  • macOS
• Cloud
  • Amazon
  • Azure
  • GCE
  • other (please specify)
• other: please specify

Eclipse Che Logs

2020-03-26 13:58:55.402 root ERROR [hosted-plugin: 50] Promise rejection not handled in one second: Error: Failed to show text document [object Object] , reason: Error: Failed to show text document [object Object]
With stack trace: Error: Failed to show text document [object Object]
    at Object.<anonymous> (/home/theia/node_modules/@theia/plugin-ext/lib/plugin/plugin-context.js:252:43)
    at step (/home/theia/node_modules/@theia/plugin-ext/lib/plugin/plugin-context.js:58:23)
    at Object.next (/home/theia/node_modules/@theia/plugin-ext/lib/plugin/plugin-context.js:39:53)
    at fulfilled (/home/theia/node_modules/@theia/plugin-ext/lib/plugin/plugin-context.js:30:58)
    at process._tickCallback (internal/process/next_tick.js:68:7) 
2020-03-26 13:58:58.454 root INFO Cannot access the registry Params: TypeError [ERR_INVALID_PROTOCOL]: Protocol "http:" not supported. Expected "https:"
    at new ClientRequest (_http_client.js:120:11)
    at Object.request (http.js:42:10)
    at RedirectableRequest._performRequest (/home/theia/node_modules/follow-redirects/index.js:169:24)
    at new RedirectableRequest (/home/theia/node_modules/follow-redirects/index.js:66:8)
    at Object.wrappedProtocol.request (/home/theia/node_modules/follow-redirects/index.js:307:14)
    at dispatchHttpRequest (/home/theia/node_modules/@eclipse-che/theia-plugin-ext/node_modules/axios/lib/adapters/http.js:180:25)
    at new Promise (<anonymous>)
    at httpAdapter (/home/theia/node_modules/@eclipse-che/theia-plugin-ext/node_modules/axios/lib/adapters/http.js:20:10)
    at dispatchRequest (/home/theia/node_modules/@eclipse-che/theia-plugin-ext/node_modules/axios/lib/core/dispatchRequest.js:59:10)
2020-03-26 13:58:58.666 root INFO Unable to read plugin registry Params: https://plugin-registry-crw-crwctl-with-proxy.apps.ocp311-2.crw/v3/plugins/ 

Additional context

[azatsarynnyy]

AxiosInstance in che-plugin-service should be configured in a similar way as it's done for che-workspace-client by the PR eclipse-che/che-workspace-client#28
cc: @vzhukovskii