Remove GitLab WAF feature from Ingress/fluentd/threat monitoring statistic pages

Why are we doing this work

More information about deprecation: #271276 (closed)

We have to remove all links/mentions/pages that are related to GitLab WAF feature:

• statistics
• cluster * fluentd

Relevant links

• Epic

Non-functional requirements

• [-] Documentation
• [-] Feature flag:
• [-] Performance:
• Testing:
  • Test if Threat Monitoring page does not include Web Application Firewall statistics and that statistics for Container Network Policy are working,
  • Test if toggle and description for WAF is not visible in Clusters -> Kubernetes -> Applications -> Ingress section and that Ingress can be installed/uninstalled,
  • Test if WAF setting for fluentd is not visible in Clusters -> Kubernetes -> Applications -> Fluentd and that Fluentd can be installed/uninstalled

Implementation plan

• frontend remove the statistics component usage with WAF and any associated WAF code
• frontend remove the cluster component, it's usage, and any associated WAF code
• frontend remove the fluentd WAF setting and any associated WAF code
• frontend view all files in #326975 (comment 545596085) to ensure no WAF code exists