Resolve "CI variables are not parameterized for alerting rules"

What does this MR do?

This MR parameterizes alerting rules and replaces variables:

• %{ci_environment_slug} with Environment#slug
• %{kube_namespace} with environment.deployment_platform&.actual_namespace
• %{environment_filter} with %{container_name!="POD",environment="#{environment.slug}"}

CE Backport: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/23335

What are the relevant issue numbers?

#7527 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• EE specific content should be in the top level /ee folder
• For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?

Closes #7527 (closed)