Merge PR from feature branch into v4-development branch for System.Text.Json serialization

[peterrsongg]

Description

**Everything in this PR has been reviewed except for the DevConfig which I added. **
This is just the PR that includes all the changes to merge into the v4-development branch PLUS two additional changes I had to make since additional PRs were merged into the v4-development branch (#3609)

4a158ba - I updated the custom SparseJsonrequest/Response marshallers to use system text json
3839ebb - This commit contains the generated changes for the protocol test related shapes (updated to use system text json)

I purposely didn't squash all the commits because each commit is a PR that has been approved and I wanted to keep that history.

Motivation and Context

Testing

Dry Run PASSED
Protocol Tests pass

dotnet test .\AWSSDK.ProtocolTests.NetFramework.csproj
Restore complete (0.7s)
  AWSSDK.CommonTest succeeded (0.1s) → C:\Dev\Repos\aws-sdk-net-staging\sdk\test\Common\bin\Debug\net472\AWSSDK.CommonTest.dll
  AWSSDK.Core.NetFramework succeeded (0.1s) → C:\Dev\Repos\aws-sdk-net-staging\sdk\src\Core\bin\Debug\net472\AWSSDK.Core.dll
  AWSSDK.Extensions.CrtIntegration.NetFramework succeeded (0.1s) → C:\Dev\Repos\aws-sdk-net-staging\extensions\src\AWSSDK.Extensions.CrtIntegration\bin\Debug\net472\AWSSDK.Extensions.CrtIntegration.dll
  AWSSDK.RestXmlProtocolNamespace.NetFramework succeeded (0.1s) → C:\Dev\Repos\aws-sdk-net-staging\sdk\test\Services\RestXmlProtocolNamespace\bin\Debug\net472\AWSSDK.RestXmlProtocolNamespace.dll
  AWSSDK.EC2Protocol.NetFramework succeeded (0.1s) → C:\Dev\Repos\aws-sdk-net-staging\sdk\test\Services\EC2Protocol\bin\Debug\net472\AWSSDK.EC2Protocol.dll
  AWSSDK.JsonProtocol.NetFramework succeeded (0.1s) → C:\Dev\Repos\aws-sdk-net-staging\sdk\test\Services\JsonProtocol\bin\Debug\net472\AWSSDK.JsonProtocol.dll
  AWSSDK.RestXmlProtocol.NetFramework succeeded (0.1s) → C:\Dev\Repos\aws-sdk-net-staging\sdk\test\Services\RestXmlProtocol\bin\Debug\net472\AWSSDK.RestXmlProtocol.dll
  ServiceClientGeneratorLib net45 succeeded (0.1s) → C:\Dev\Repos\aws-sdk-net-staging\generator\ServiceClientGeneratorLib\bin\Debug\net45\ServiceClientGeneratorLib.dll
  AWSSDK.JSONRPC10.NetFramework succeeded (0.1s) → C:\Dev\Repos\aws-sdk-net-staging\sdk\test\Services\JSONRPC10\bin\Debug\net472\AWSSDK.JSONRPC10.dll
  AWSSDK.S3.NetFramework succeeded (0.2s) → C:\Dev\Repos\aws-sdk-net-staging\sdk\src\Services\S3\bin\Debug\net472\AWSSDK.S3.dll
  AWSSDK.QueryProtocol.NetFramework succeeded (0.3s) → C:\Dev\Repos\aws-sdk-net-staging\sdk\test\Services\QueryProtocol\bin\Debug\net472\AWSSDK.QueryProtocol.dll
  AWSSDK.UnitTestUtilities.NetFramework succeeded (0.4s) → C:\Dev\Repos\aws-sdk-net-staging\sdk\test\UnitTests\Custom\bin\Debug\net472\AWSSDK.UnitTestUtilities.dll
  AWSSDK.RestJsonProtocol.NetFramework succeeded (0.7s) → C:\Dev\Repos\aws-sdk-net-staging\sdk\test\Services\RestJsonProtocol\bin\Debug\net472\AWSSDK.RestJsonProtocol.dll
  AWSSDK.ProtocolTests.NetFramework succeeded (0.5s) → bin\Debug\net472\AWSSDK.ProtocolTests.NetFramework.dll
  AWSSDK.ProtocolTests.NetFramework test succeeded (3.0s)

Test summary: total: 610, failed: 0, succeeded: 588, skipped: 22, duration: 3.0s
Build succeeded in 5.7s

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project
• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have read the README document
• I have added tests to cover my changes
• All new and existing tests passed

License

• I confirm that this pull request can be released under the Apache 2 license

[dscpinheiro]

This doesn't seem correct. Perhaps your merge picked the wrong files to keep?

[peterrsongg]

yup must've gotten lost in the rebase. will add both back

[dscpinheiro]

Indentation looks off here.

[peterrsongg]

good catch, will fix in next rev.