[Instrumentation.AWS, Extensions.AWSXRay] Add net6.0 target, replace net452 target with net462

[wjrogers]

Fixes #1078.

Changes

Add a net6.0 target to OpenTelemetry.Contrib.Instrumentation.AWS and OpenTelemetry.Contrib.Extensions.AWSXRay. Also, update the former's out-of-support net452 target to net462, i.e. NetFrameworkMinimumSupportedVersion. I combined the updates to these two projects into one PR because the latter is a dependency of the former.

• Update conditional compilation symbols in tests project(s) from NET452 to NETFRAMEWORK.
• Add a net7.0 test target to Instrumentation.AWS.Tests to match Extensions.AWSXRay.Tests.
• Add a netcoreapp3.1 test target to Extensions.AWSXRay to exercise the library's netstandard2.0 target.
• In tests projects, suppress the build warning generated by System.Diagnostics.DiagnosticSource 7.0.0 when targeting out-of-support frameworks. (See Discussion: netstandard2.0 packages don't compile for out-of-support runtimes opentelemetry-dotnet#3448 for discussion.)
• Fix warnings from analyzers enabled by the new target. I tried to minimize the necessary code changes and add tests where I needed to make a non-trivial change.
• Remove now-unnecessary reference to System.Net.Http.

[vishweshbankwar]

@wjrogers We are working towards removing un-supported versions(#1031) from the repo including unit test. netcoreapp3.1 is out of support. Is there any specific reason you want to add netcoreapp3.1?

[wjrogers]

@vishweshbankwar I noticed that no tests were run for the netstandard2.0 target and that Instrumentation.AWS.Tests already had a netcoreapp3.1 test target, so I added the same target to Extensions.AWSXRay.Tests so that the tests would run against the netstandard2.0 library assembly. There is some context in the issue I linked about the difficulty of keeping netstandard2.0 targets when every supported runtime will bind to a more-specific target (in this case, net6.0+ to net6.0 and net462+ to net462). I am happy to remove it if you prefer, but that will mean the netstandard2.0 build is untested.

Personally, given the fact there are no more supported runtimes that need it, I think it makes more sense to remove the netstandard2.0 target from the library and provide only more-specific builds (net6.0 and net462), but I didn't want to make that decision for you!

[cijothomas]

@wjrogers Can you describe the reason why you are adding net6.0 target? Are you leveraging any new APIs/Features from net6.0?

[wjrogers]

@cijothomas Sure. This PR is meant to combine with #1092 to remove a dependency when targeting net6.0 or newer. My hope is to avoid taking a dependency on Newtonsoft.Json when I use this package in my own work. net6.0 is the oldest supported runtime that includes System.Text.Json.

It's not strictly required to target net6.0 — the reference to System.Text.Json would be enough — but I find it helpful when installing packages to see the minimal list of dependencies for each supported target framework. If that's not enough justification, I'd be happy to prepare a new PR that just bumps the minimum framework version for Instrumentation.AWS.

[cijothomas]

@wjrogers Thanks for the explanation. Could you update the PR description so its easy to why is this needed. And also I'd suggest to make the net452->net462 into a separate PR of its own.

[wjrogers]

I'd suggest to make the net452->net462 into a separate PR of its own.

Have now done so as #1095. I will refresh this PR to isolate the net6.0 addition later tonight or tomorrow. Thanks for the feedback!

[wjrogers]

I am closing this PR so I can push a new branch that affects only Extensions.AWSXRay, with a more interesting justification. I will follow up on Instrumentation.AWS if/when my other PRs are accepted.

[wjrogers]

continued in #1096