Add E2E test of web terminal file sync

What does this MR do?

Adds an E2E test of the Web IDE web terminal file sync.

Creates a kubernetes cluster with a runner to use to run the web terminal with the file sync service enabled.

Closes gitlab-org/quality/testcases#86

Limitations

• The web terminal is a canvas element so we can't easily check that files sync, we can only check that the UI reports that syncing is enabled.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team