[telegraf] Add support for Cisco Model-Driven Telemetry (cisco_telemetry_mdt)

[hampusehh]

Automatically expose Cisco Model-Driven Telemetry (MDT) port as defined in config.inputs.

config:
  inputs:
    - cisco_telemetry_mdt:
         service_address: ":57000"

- [ ] CHANGELOG.md updated
- [x] Rebased/mergable
- [ ] Tests pass
- [x] Sign [CLA](https://influxdata.com/community/cla/) (if not already signed)

[Saigut]

Hello, why not merge this pr?

[joelsvensson]

Can we try to bump the chart version similar to previous PRs?
https://github.com/influxdata/helm-charts/pull/390/files
https://github.com/influxdata/helm-charts/pull/401/files
Commit message like "feat: [telegraf] add support for cisco_telemetry_mdt input" and tests might run too.

Hopefully this can get it to a better state and bring attention to reviewers.
Current list of maintainers is outdated:
https://github.com/influxdata/helm-charts/blob/master/charts/telegraf/Chart.yaml#L18-L22

[hampusehh]

@gitirabassi, is it possible for you to look at this? Or help us get attention here?
(I ping you as you are one of the maintainers of the Chart.yaml)

[joelsvensson]

@gitirabassi, is it possible for you to look at this? Or help us get attention here? (I ping you as you are one of the maintainers of the Chart.yaml)

Maybe @powersj can assist?

[hamps-contrib]

LGTM

[hamps-contrib]

LGTM; after rebase