Update VendorHttpApiRequestor to use support http client library

[nrcventura]

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

In newer versions of .net the usage of WebRequest.Create is deprecated. We should update this code to either leverage the code that we use for sending requests to New Relic, or update it to use the current code for .net framework, and HttpClient for netstandard.

See

newrelic-dotnet-agent/src/Agent/NewRelic/Agent/Core/Utilization/VendorHttpApiRequestor.cs

Line 20 in 0be7ccd

var request = WebRequest.Create(uri);

for a reference to the code that makes these requests.

Acceptance Criteria

• On .net framework HttpWebRequest should be used
• On netstandard builds of the agent HttpClient should be used

Dependencies

• None

Describe Design Consideration/Limitations

Additional context

Estimates

Please provide initial t-shirt size
M

[workato-integration]

https://new-relic.atlassian.net/browse/NR-276378