Extend Guard config to continuously run specs under ee directory

What does this MR do?

This change makes it possible to continuously run specs under ee/ directory. I tried to keep the configuration DSL as similar as possible to previous version.

Note: I also tried the chdir option of guard but it didn't work somehow and this was the easiest solution came to my mind.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

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