Add functional end-to-end tests for the chart

[tigrannajaryan]

We need to test the Helm chart's functionality end-to-end:

• Install the chart on a test Kubernetes cluster.
• Run a test mock backend (can possibly reuse mock backends from Collector testbed).
• Configure the chart to send collected traces, metrics and logs to the mock backend.
• Run some test workload on the cluster. The workload should generate telemetry: application traces, metrics and logs and cluster metrics and logs.
• Let mock backend to receiver generated telemetry and compare against expected data. It would be best that expected data is defined in a set of golden files.

Make sure end-to-end test is run on Github action as part of every PR and main branch build.

[tigrannajaryan]

Looks like we are already using https://github.com/helm/chart-testing-action which supposedly is what we need to install the chart, so probably step 1 above is already covered.