Move empty state into the threat monitoring tabs

What does this MR do?

Move empty state into the threat monitoring tabs

• with the addition of the alerts tab, which does not need an environment set up for the project, move the empty state, that is shown when an invalid environment id is provided, into the tabs that require an environment
• update tests

Screenshots (strongly suggested)

Scenario	Before	After
no environment
with environment		Same

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

Related to #296179 (closed)