Add new metrics related to jobs requesting and API usage

What does this MR do?

Adds few new metrics related to API communication and jobs requesting.

Example of added metrics:

# HELP ci_runner_api_request_statuses_total The total number of api requests, partitioned by runner, endpoint and status.
# TYPE ci_runner_api_request_statuses_total counter
ci_runner_api_request_statuses_total{endpoint="patch_trace",runner="84630054",status="202"} 2
ci_runner_api_request_statuses_total{endpoint="request_job",runner="84630054",status="201"} 1
ci_runner_api_request_statuses_total{endpoint="request_job",runner="84630054",status="204"} 31
ci_runner_api_request_statuses_total{endpoint="request_job",runner="cd835fa2",status="204"} 4
ci_runner_api_request_statuses_total{endpoint="update_job",runner="84630054",status="200"} 2
# HELP ci_runner_request_concurrency The current number of concurrent requests for a new job
# TYPE ci_runner_request_concurrency gauge
ci_runner_request_concurrency{runner="84630054"} 10
ci_runner_request_concurrency{runner="cd835fa2"} 1
# HELP ci_runner_request_concurrency_exceeded_total Counter tracking exceeding of request concurrency
# TYPE ci_runner_request_concurrency_exceeded_total counter
ci_runner_request_concurrency_exceeded_total{runner="84630054"} 0
ci_runner_request_concurrency_exceeded_total{runner="cd835fa2"} 53

Why was this MR needed?

To get more knowledge about how configuration parameters are affecting jobs requesting.

Are there points in the code the reviewer needs to double check?

Does this MR meet the acceptance criteria?

• Documentation created/updated
• Tests
  • Added for this feature/bug
  • All builds are passing
• Branch has no merge conflicts with master (if you do - rebase it please)

What are the relevant issue numbers?