Add method label to status counter metrics

What does this MR do?

Add method label to status counter metrics

• #38654 (closed)
• Add method label to status counter metric to add granularity to metrics collected. This is part of a wider effort to enhance the runner observability.

# TYPE gitlab_runner_api_request_statuses_total counter
gitlab_runner_api_request_statuses_total{endpoint="patch_trace",method="patch",runner="kjaPK1kMw",status="202",system_id="s_760931104d8c"} 2
gitlab_runner_api_request_statuses_total{endpoint="request_job",method="post",runner="kjaPK1kMw",status="201",system_id="s_760931104d8c"} 1
gitlab_runner_api_request_statuses_total{endpoint="request_job",method="post",runner="kjaPK1kMw",status="204",system_id="s_760931104d8c"} 3
gitlab_runner_api_request_statuses_total{endpoint="update_job",method="put",runner="kjaPK1kMw",status="200",system_id="s_760931104d8c"} 1
gitlab_runner_api_request_statuses_total{endpoint="update_job",method="put",runner="kjaPK1kMw",status="202",system_id="s_760931104d8c"} 1

Why was this MR needed?

Increase runner client request-response observability.

What's the best way to test this MR?

go test ./network/...

What are the relevant issue numbers?

#38654 (closed)