Add Web Terminal tab in cluster configuration page

Description

Allow cluster admin to provide default image and/or timeout period for all cluster users

Acceptance Criteria

1. Add Web Terminal tab in Cluster Configuration page under Developer tab
2. This tab should be visible only to cluster admins
3. Add 2 fields, one is to change  default timeout and other is to change default image
4. Default values should be pre-populated in above fields from

Default Timeout -  WEB_TERMINAL_IDLE_TIMEOUT environment variable's value in the web-terminal-exec DevWorkspaceTemplate
Default Image - .spec.components[].container.image field in the web-terminal-tooling DevWorkspaceTemplate

      5. Once user change this and save, need to update the same above resources(refer comment in epic https://issues.redhat.com/browse/ODC-7119 for more details)

      6. If the user has read access to DevWorkspaceTemplate, then save button should not be enabled and if user don't have read access to DevWorkspaceTemplate then no need to show web terminal tab in configuration page

      7. Add e2e tests

Additional Details:

Timeout and Image component should be similar to web terminal components (attached in ticket).
refer comment in epic https://issues.redhat.com/browse/ODC-7119 for more details