Change AccountService from Go to DotNet (auto)

[RassK]

Changes

Fixes #589

Changes AccountingService from Go to .NET service. Uses OpenTelemetry .NET Automatic Instrumentation.

NOTE: It's a first preview of demo app that is instrumented with OpenTelemetry .NET Automatic instrumentation. Some parts are still TBD. Please review and add comments about improvements and missing parts / docs.

Merge Requirements

For new features contributions please make sure you have completed the following essential items:

• [x] CHANGELOG.md updated to document new feature additions
• [x] Appropriate documentation updates in the docs
• [ ] Appropriate Helm chart updates in the helm-charts

Maintainers will not merge until the above have been completed. If you're unsure which docs need to be changed ping the @open-telemetry/demo-approvers.