The Cloudflare Exporter Prometheus exporter has not worked for 9 months+

The cloudflare_exporter https://gitlab.com/gitlab-org/cloudflare_exporter has not been working correctly for 9 months or more.

This is leading to the WAF dashboard having no data: https://dashboards.gitlab.net/d/waf-main/waf-overview?orgId=1

The exporter is running, but is failing to scrape Cloudflare.

See https://thanos.gitlab.net/graph?g0.expr=increase(cloudflare_graphql_scrape_errors_total%5B5m%5D)&g0.tab=0&g0.stacked=0&g0.range_input=1y&g0.max_source_resolution=auto&g0.deduplicate=1&g0.partial_response=0&g0.store_matches=%5B%5D for example.

Having improved Cloudflare monitoring is a potential corrective action for production#8457 (closed) in that failures at the Cloudflare level could potentially have picked up this problem (or helped in picking it up).

cc @gitlab-com/gl-infra/sre-observability @f_santos @T4cC0re

Acceptance Criteria:

• switch exporter to https://github.com/lablabs/cloudflare-exporter
• Update proper SLIs for the WAF service and make sure alerts go to g_infra_foundations channel