Eliminate redundant user-facing docs from /docs

[theletterf]

Now that #5365 has been completed, we could remove those user-facing docs from the /docs folder. Happy to help with that.

https://opentelemetry.io/docs/languages/dotnet/

[cijothomas]

@theletterf I didn't follow the full PR, but can you confirm if the entire contents were lifted-and-shifted to the docs page?
I was checking for https://github.com/open-telemetry/opentelemetry-dotnet/tree/main/docs/metrics#cardinality-limits and could not find it it in the docs.

Lets make sure every content is copied to docs page, and then nuke this whole directory.

[theletterf]

Opened a new PR to address the Best practices that were missing: open-telemetry/opentelemetry.io#7543

Current situation:

Source File (from XML)	Repository File
docs/diagnostics/experimental-apis/OTEL1000.md	(skipped)
docs/diagnostics/experimental-apis/OTEL1001.md	(skipped)
docs/diagnostics/experimental-apis/OTEL1004.md	(skipped)
docs/diagnostics/experimental-apis/README.md	(skipped)
docs/diagnostics/README.md	(skipped)
docs/logs/complex-objects/README.md	content/en/docs/languages/dotnet/logs/complex-objects.md
docs/logs/correlation/README.md	content/en/docs/languages/dotnet/logs/correlation.md
docs/logs/customizing-the-sdk/README.md	(skipped)
docs/logs/dedicated-pipeline/README.md	content/en/docs/languages/dotnet/logs/dedicated-pipeline.md
docs/logs/extending-the-sdk/README.md	(skipped)
docs/logs/getting-started-aspnetcore/README.md	content/en/docs/languages/dotnet/logs/getting-started-aspnetcore.md
docs/logs/getting-started-console/README.md	content/en/docs/languages/dotnet/logs/getting-started-console.md
docs/logs/redaction/README.md	content/en/docs/languages/dotnet/logs/redaction.md
docs/logs/README.md	content/en/docs/languages/dotnet/logs/_index.md
docs/metrics/customizing-the-sdk/README.md	(skipped)
docs/metrics/exemplars/README.md	content/en/docs/languages/dotnet/metrics/exemplars.md
docs/metrics/extending-the-sdk/README.md	(skipped)
docs/metrics/getting-started-aspnetcore/README.md	content/en/docs/languages/dotnet/metrics/getting-started-aspnetcore.md
docs/metrics/getting-started-console/README.md	content/en/docs/languages/dotnet/metrics/getting-started-console.md
docs/metrics/getting-started-prometheus-grafana/README.md	content/en/docs/languages/dotnet/metrics/getting-started-prometheus-grafana.md
docs/metrics/learning-more-instruments/README.md	content/en/docs/languages/dotnet/metrics/instruments.md
docs/metrics/README.md	content/en/docs/languages/dotnet/metrics/_index.md
docs/resources/README.md	content/en/docs/languages/dotnet/resources.md
docs/trace/customizing-the-sdk/README.md	(skipped)
docs/trace/extending-the-sdk/README.md	(skipped)
docs/trace/getting-started-aspnetcore/README.md	content/en/docs/languages/dotnet/traces/getting-started-aspnetcore.md
docs/trace/getting-started-console/README.md	content/en/docs/languages/dotnet/traces/getting-started-console.md
docs/trace/getting-started-jaeger/README.md	content/en/docs/languages/dotnet/traces/jaeger.md
docs/trace/links-based-sampler/README.md	content/en/docs/languages/dotnet/traces/links-based-sampler.md
docs/trace/links-creation-with-new-activities/README.md	content/en/docs/languages/dotnet/traces/links-creation.md
docs/trace/reporting-exceptions/README.md	content/en/docs/languages/dotnet/traces/reporting-exceptions.md
docs/trace/stratified-sampling-example/README.md	content/en/docs/languages/dotnet/traces/stratified-sampling.md
docs/trace/tail-based-sampling-span-level/README.md	content/en/docs/languages/dotnet/traces/tail-based-sampling.md
docs/trace/README.md	content/en/docs/languages/dotnet/traces/_index.md
docs/README.md	content/en/docs/languages/dotnet/_index.md

[Kielek]

Looking forward for the PR, you can consider one generic README file with link to the new location :- )

[theletterf]

@Kielek Now that I think of it, I'm not so sure we can delete a lot, unless we're OK with also getting rid of the .cs examples. Are we? The alternative is to replace the contents of each README with a link to the docs.