Add response time and endpoint counters as metrics for Mira

[wennmo]

This is related to #227.

I have added metrics for measuring response time in milliseconds for all requests to Mira. If a response takes more than MIRA_ALLOWED_RESPONSE_TIME (default 1 second), Mira will log a warning.

Also added counters for all endpoints in Mira.

# HELP mira_api_response_time_ms Time in milliseconds consumed from Mira receiving a request until a response is sent
# TYPE mira_api_response_time_ms summary
mira_api_response_time_ms{quantile="0.01"} 0
mira_api_response_time_ms{quantile="0.05"} 0
mira_api_response_time_ms{quantile="0.5"} 0.7142857142857143
mira_api_response_time_ms{quantile="0.9"} 5
mira_api_response_time_ms{quantile="0.95"} 5.75
mira_api_response_time_ms{quantile="0.99"} 6
mira_api_response_time_ms{quantile="0.999"} 6
mira_api_response_time_ms_sum 15
mira_api_response_time_ms_count 15

# HELP mira_api_engines_request_counter Number of requests to /engines endpoint
# TYPE mira_api_engines_request_counter counter
mira_api_engines_request_counter 8

# HELP mira_api_health_request_counter Number of requests to /health endpoint
# TYPE mira_api_health_request_counter counter
mira_api_health_request_counter 6

# HELP mira_api_metrics_request_counter Number of requests to /metrics endpoint
# TYPE mira_api_metrics_request_counter counter
mira_api_metrics_request_counter 2

[peol]

Nice, good work.

[FredrikFolkesson]

LGTM, one minor change if possible

[FredrikFolkesson]

can we do this with async await?