`Programming exercises`: Allow online editor in read-only mode

[b-fein]

Is your feature request related to a problem?

Currently, programming exercises allow the activation of the online editor and/or the offline IDE. This sometimes leads to a conflict in case inexperienced students make submissions in both and then have to solve the merge conflicts.

Describe the solution you'd like

I would like to be able to activate the online editor in read-only mode if the offline IDE mode is enabled.

This would prevent such conflicts. Additionally,

• this would enable students see the location for static code analysis issues inline,
• students would be able to browse the repository in cases where they don’t have direct access to the version control system (e.g., GitLab using access tokens, local-VCS).

Describe alternatives you've considered

No response

Additional context

The online editor already supports a read-only mode for the manual assessment and review after the deadline.

[b-fein]

Discussion on Slack about an alternative solution:

• LocalVCS supports a read-only view of the repository (#7957):
• This feature should be visible for GitLab setups as well.
• The feature may be gated behind a config flag in the server settings so that it can be enabled or disabled by an admin.

[dfuchss]

Related to https://github.com/ls1intum/Artemis/issues/5025 . A Read-Only mode would be nice for exam reviews as well :)