feat: add dataplane metrics label

[pmalek]

What this PR does / why we need it:

This PR adds dataplane metrics label to account for KIC sending configuration to more than 1 gateway.

The outcome of this PR will be that users will see separate time series for each dataplane for the following metrics:

• ingress_controller_configuration_push_count
• ingress_controller_configuration_push_duration_milliseconds

Which issue this PR fixes:

Fixes #3417

Special notes for your reviewer:

Blocked by #3421

This will make it so all ingress_controller_configuration_push_count and ingress_controller_configuration_push_duration_milliseconds time series will change. Regardless of running SCD or not. If we'd like to retain the current behaviour (not include the label) then we'd need to tweak this PR to account for this, i.e.:

• don't add dataplane label when running with 1 Gateway, communicating through localhost/127.0.0.1
• add it when running in SCD mode

PR Readiness Checklist:

Complete these before marking the PR as ready to review:

• the CHANGELOG.md release notes have been updated to reflect any significant (and particularly user-facing) changes introduced by this PR

[codecov]

Codecov Report

Base: 72.4% // Head: 72.5% // Increases project coverage by +0.1% 🎉

Coverage data is based on head (7c3e134) compared to base (22f6bad).
Patch coverage: 100.0% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #3521     +/-   ##
=======================================
+ Coverage   72.4%   72.5%   +0.1%     
=======================================
  Files        120     121      +1     
  Lines      14318   14357     +39     
=======================================
+ Hits       10369   10422     +53     
+ Misses      3284    3274     -10     
+ Partials     665     661      -4     

Impacted Files	Coverage Δ
internal/dataplane/deckerrors/conflict.go	100.0% <100.0%> (ø)
internal/dataplane/kong_client.go	85.0% <100.0%> (-0.2%)	⬇️
internal/dataplane/sendconfig/sendconfig.go	77.2% <100.0%> (-6.1%)	⬇️
internal/metrics/prometheus.go	100.0% <100.0%> (ø)
internal/dataplane/parser/parser.go	91.5% <0.0%> (+0.8%)	⬆️
internal/dataplane/kongstate/service.go	67.3% <0.0%> (+1.2%)	⬆️
...ternal/controllers/gateway/httproute_controller.go	71.6% <0.0%> (+1.8%)	⬆️

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[czeslavo]

If we'd like to retain the current behaviour (not include the label) then we'd need to tweak this PR to account for this

IMO we should be fine with adding the label and not adjusting it to the SCD in any special way. I think it's better to have it consistent across deployment modes.

Note: we need to update https://docs.konghq.com/kubernetes-ingress-controller/latest/references/prometheus/.

[pmalek]

If we'd like to retain the current behaviour (not include the label) then we'd need to tweak this PR to account for this

IMO we should be fine with adding the label and not adjusting it to the SCD in any special way. I think it's better to have it consistent across deployment modes.

👍

Note: we need to update https://docs.konghq.com/kubernetes-ingress-controller/latest/references/prometheus/.

Good catch, I'll add that to the related issue.