Replace existing .NET layerless steps with better ones that do not include using the layer.

[jaffinito]

Describe the story, please be clear on scope of the story.

Replace existing .NET layerless steps with better ones that do not include using the layer.
Should include:

• .NET Agent automatically instruments most AWS Lambda functions
• Enters a "serverless mode" that disables sending data to New Relic directly as well as several other features.
• Mention relying on New Relic Lambda Extension or the newrelic-log-ingestion lambda function.
• Install via nuget or manually
• Setting env vars

Relates to newrelic/docs-website#17765

Acceptance Criteria

PR with docs changes that address layerless installs.

[workato-integration]

https://new-relic.atlassian.net/browse/NR-287209