Add alert related labels to CiliumNetworkPolicies

What does this MR do?

Add alert related labels to CiliumNetworkPolicies. The label will contain the project id which will be used to correlate the network policy into its respective project within agentk. This is going to be applicable for both new and existing policies.

Apart from being visible as part of the yaml preview, this change works transparently from the user perspective.

AgentK related MR: gitlab-org/cluster-integration/gitlab-agent!252 (merged)

Related issue: #294426 (closed)

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