feat: fix dangaling metrics regading status code

[y-eight]

Motivation

Referes to https://github.com/caas-team/sparrow/issues/133

Changes

The metric sparrow_latency_duration_seconds will now be clear before the new duration with label status is exposed. Dangling metrics that do not show the current status are cleared up.

Additionally, I have introduced two new metrics like @puffitos suggested.

• sparrow_latency_seconds
• sparrow_latency_count (old sparrow_latency_count has been renamed to sparrow_latency_total_count)

For additional information look at the commits.

Tests done

• [x] Unit tests succeeded
• [x] E2E tests succeeded

First run:

# TYPE sparrow_latency_duration_seconds gauge
sparrow_latency_duration_seconds{status="200",target="https://gitlab.devops.telekom.de"} 0.222653973
sparrow_latency_duration_seconds{status="200",target="https://httpstat.us/random/200,500-504"} 0.711660485
sparrow_latency_duration_seconds{status="418",target="https://yam.telekom.de"} 0.214198665

Second run:

# TYPE sparrow_latency_duration_seconds gauge
sparrow_latency_duration_seconds{status="200",target="https://gitlab.devops.telekom.de"} 0.24624422
sparrow_latency_duration_seconds{status="418",target="https://yam.telekom.de"} 0.212984192
sparrow_latency_duration_seconds{status="502",target="https://httpstat.us/random/200,500-504"} 0.69023805

TODO

• [x] I've assigned this PR to myself
• [x] I've labeled this PR correctly

[puffitos]

@y-eight I've added a simple hint, which metric will replace the deprecated one.