Better method to detect helm chart version in template tests

[kasia-kujawa]

It would be good to have better method to detect helm chart version in helm templates. Sometimes container image can have same image tag as our helm chart, in current form of template tests this container tag will be replaced to %CURRENT_CHART_VERSION%

related to #3626

[sumo-drosiek]

There is limited number of cases:

➜  sumologic-kubernetes-collection git:(main) ✗ grep '%CURRENT_CHART_VERSION%' -hR tests/helm/testdata/goldenfile | sed 's/^ *//;' | sort | uniq
app.kubernetes.io/version: "%CURRENT_CHART_VERSION%"
chart: "sumologic-%CURRENT_CHART_VERSION%"
chart: sumologic-%CURRENT_CHART_VERSION%
client: k8s_%CURRENT_CHART_VERSION%
description = "Sumo Logic Kubernetes Collection\nversion: %CURRENT_CHART_VERSION%"