Add Splunk .NET docker image to the chart

[atoulme]

Description:
Add Splunk .NET docker image to the chart. Add to rotation for image updates.

[pjanotti]

LGTM, just need to wait for us to publish the Docker image.

[Kielek]

I think that you are missing, one important thing.
Operator has to setup env. var.: "OTEL_DOTNET_AUTO_PLUGINS": "Splunk.OpenTelemetry.AutoInstrumentation.Plugin, Splunk.OpenTelemetry.AutoInstrumentation"

Otherwise it will be working us Vanilla/upstream distribution.

There will be no support for RUM, realms/splunk access key, AlwaysOn Profiling (in progress), come gdi-config requierments.

[Kielek]

Changes looks good to me, but didn't have chance to test it E2E. I hope you have did it.

Two more thing

1. Should we update our procedure to include changes in this repository? https://github.com/signalfx/splunk-otel-dotnet/blob/608f45e960eb6f6af55c0554a21e40527f20faa8/RELEASING.md Or it willl be on your side? What is the typical scenario?
2. Minor comment related to the changelog entry.

[atoulme]

Should we update our procedure to include changes in this repository? https://github.com/signalfx/splunk-otel-dotnet/blob/608f45e960eb6f6af55c0554a21e40527f20faa8/RELEASING.md Or it willl be on your side? What is the typical scenario?
We run a cron job to pick up new versions, and open a PR automatically. We do this for java and nodejs already. This PR adds the dotnet image to the rotation.

[atoulme]

Should we add a test application similar to node.js? @jvoravong wdyt?

[jvoravong]

Was able to verify the Splunk .NET docker image works e2e. There is an issue in .NET environments where the exporter endpoint isn't always respected properly which I will address in #1117.

Merging this PR now.