[prometheus-blackbox-exporter] optional set path per target

[itsmethemojo]

What this PR does / why we need it

This adds the option to set the path per target if needed when creating service monitors for the blackbox exporter. When testing multiple domains and pathes with one blackbox exporter chart installation this will help.

Which issue this PR fixes

none

Special notes for your reviewer

Checklist

• DCO signed
• Chart Version bumped
• Title of the PR starts with chart name (e.g. [prometheus-couchdb-exporter])

[itsmethemojo]

i actually do not understand if the unittest task is mandatory here because only a couple of charts do have unittests

should i add tests only for this feature for the chart prometheus-blackbox-exporter?

$ ls -1 -R | grep unit
unittests
./charts/alertmanager/unittests:
unittests
unittests
./charts/kube-prometheus-stack/charts/crds/unittests:
./charts/kube-prometheus-stack/unittests:
./charts/kube-prometheus-stack/unittests/alertmanager:
./charts/kube-prometheus-stack/unittests/exporters:
./charts/kube-prometheus-stack/unittests/exporters/kube-scheduler:
./charts/kube-prometheus-stack/unittests/grafana:
./charts/kube-prometheus-stack/unittests/prometheus:
./charts/kube-prometheus-stack/unittests/prometheus-operator:
./charts/kube-prometheus-stack/unittests/thanos-ruler:
unittests
./charts/kube-state-metrics/unittests:
unittests
./charts/prom-label-proxy/unittests:
unittests
./charts/prometheus-kafka-exporter/unittests:

UPDATE i looked up how previous PRs in this chart handlet it and removed the unit test checkbox