[dns-exporter] adds podMonitor resource

[bb-Ricardo]

What this PR does / why we need it

Adds the monitoring.googleapis.com/v1 PodMonitor resource additionally to serviceMonitor.

Which issue this PR fixes

• currently it is not possible to use dns-exporter with the Google Prometheus instance which uses PodMonitor resources

Special notes for your reviewer

Checklist

• [ ] Target a branch starting with dev-
• [x] Chart Version bumped
• [x] Title of the PR starts with chart name (e.g. [baserow])

[bb-Ricardo]

@christianhuth I opened some PRs with improvements for the dns-exporter

• #2255
• #2252
• #2251
• #2250

I could also merge them together into one PR. What do you prefer?

[christianhuth]

Amazing work @bb-Ricardo

I will check them this week. No need to merge them into one.

[bb-Ricardo]

great, thank you very much

A few things to consider regarding this PR:

• I bumped the version to 2.0.0 as it moves serviceMonitor.modules to modulesConfig because serviceMonitor and podMonitor share the same module config and therefore breaks existing configurations
• this PR changes the implementation in #2252 (https://github.com/christianhuth/helm-charts/pull/2252/files#diff-cd9310b70e26877a89d2aa235d38a5adf770b194955d879a5235b7c4a4f4cefbR17)
• dns-exporter had an issue (https://github.com/tykling/dns_exporter/pull/174) and I'm still waiting for a new release