Resolve runner ignores request_concurrency

What does this MR do?

This MR adds a check to confirm if the deprecated RUNNER_REQUEST_CONCURRENCY is configured and allow the same to be configured in the config section in the values.yaml e.g.

config: |
    [[runners]]
      request_concurrency = 5

Why was this MR needed?

It should be possible to override the request_concurrency field if set in the config section

What's the best way to test this MR?

• Setting runners.requestConcurrency will override the value in the config section (current behavior)

  requestConcurrency: 10
  config: |
    [[runners]]
      request_concurrency = 5

kubectl exec -it gitlab-runner-gitlab-runner-xxx -- cat /home/gitlab-runner/.gitlab-runner/config.toml

[session_server]
  session_timeout = 1800

[[runners]]
  name = "gitlab-runner-gitlab-runner-xxx-xxx"
  output_limit = 16384
  request_concurrency = 10

• Set request_concurrency in the config section of the values file and ensure the deprecated field is commented out

# requestConcurrency: 10
  config: |
    [[runners]]
      request_concurrency = 5

• Confirm that this has been passed on to the configMap

  kubectl describe configmaps gitlab-runner-gitlab-runner

...
config.template.toml:
----
[[runners]]
  request_concurrency = 5
...

• The correct value is passed to the /home/gitlab-runner/.gitlab-runner/config.toml

  kubectl exec -it gitlab-runner-gitlab-runner-xxx -- cat /home/gitlab-runner/.gitlab-runner/config.toml

[[runners]]
  name = "gitlab-runner-gitlab-runner-xxxx-xxx"
  output_limit = 16384
  request_concurrency = 5

What are the relevant issue numbers?

Closes #267 (closed)