Gwt ide in sidecar is not working due to CORS configuration on ws-agent

[skabashnyuk]

Description

Ws-agent by default set cors filter configuration to allow request only from che.api. But if gwt ide running as sidecar it loads IDE not from the master but from a different server running in the dedicated container.
We need to change default cors logic to be more similar to workspace loader. https://github.com/eclipse/che/blob/master/workspace-loader/src/index.ts#L349-L361
It should detect ide location from servers configuration or fallback to ide attribute of workspace configuration.

Reproduction Steps

• Enable GWT Editor

• Start workspace
• Try to create project

• In console you can see CORS errors