Move fuzz license check to .pre stage

What does this MR do?

Moves the license check to the .pre stage so that the stage is guaranteed to exist. The current template will fail if the user has not defined a test stage.

Discussion in Slack for additional background.

Open question: Would this check be better done in the fuzz stage? It wouldn't necessarily run before the fuzz test job itself in that case but the fuzz stage would also exist since the template is being included.

Screenshots (strongly suggested)

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

Availability 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
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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