Add summarized gitaly apdex for usage ping

What does this MR do?

Adds a 5 minute summarised apdex rule for gitaly so that it can be queried from usage ping.

Related issues

gitlab#216683 (closed)

Testing (GDK)

Enable prometheus: gdk.yml:

prometheus:
  enabled: true

Rejigger gdk:

gdk reconfigure

Turn on gitaly' prometheus metrics port and histogram latencies: gitaly/gitaly-0.praefect.toml:

# Optional: export metrics via Prometheus
prometheus_listen_addr = "127.0.0.1:9236"

[prometheus]
grpc_latency_buckets = [0.001, 0.005, 0.025, 0.1, 0.5, 1.0, 10.0, 30.0, 60.0, 300.0, 1500.0]

Download and setup gitlab prometheus rules from omnibus:

curl https://gitlab.com/gitlab-org/omnibus-gitlab/-/raw/usage_ping_gitaly_apdex/files/gitlab-cookbooks/monitoring/templates/rules/gitlab.rules?inline=false -o <GDK_ROOT>/prometheus/gitlab.rules 

prometheus/prometheus.yml:

rule_files:
  - 'gitlab.rules'

Procfile:

prometheus: exec docker run -p 9090:9090 -v <GDK_ROOT>/prometheus/prometheus.yml:/etc/prometheus/prometheus.yml -v <GDK_ROOT>/prometheus/gitlab.rules:/etc/prometheus/gitlab.rules prom/prometheus:v2.25.0

Restart GDK:

gdk restart

Check that prometheus has detected our gitaly target as healthy in http://localhost:9090/targets:

Make some git activity. The rule should now have data.

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion

Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• Pipeline is green on dev.gitlab.org if the change is touching anything besides documentation or internal cookbooks
• trigger-package has a green pipeline running against latest commit

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for the GitLab Chart opened