Remove usage of jsonutil

[ShelbyZ]

Summary

Remove our usage of jsonutil.BuildJSON, etc and the imports to "github.com/aws/aws-sdk-go/private/protocol/json/jsonutil" from various code locations. For aws-sdk-go-v2 we do not have access to special JSON parsing and should rely on encoing/json.

Implementation details

1. Remove github.com/aws/aws-sdk-go/private/protocol/json/jsonutil imports
2. Replace jsonutil.BuildJSON usage with json.Marshal
3. Replace jsonutil. UnmarshalJSON usage with json.Unmarshal
4. Update awssdk.go (code generation for api clients) to replace locationName with json to align struct properties
5. Update awssdk.go to add omitempty to struct properties that are not marked required:true
6. Create new utils.go (ecs-agent) methods to handle serialization/deserialization based on aws-sdk-go v1 patterns to avoid issues with time.Time needing to be UTC seconds and not a timestamp string
7. Add testing around new utils.go methods
8. Regenerate api.go files (make gogenerate) to update acs/tcs APIs
9. Cast time.Time to Timestamp where required (alias type)

Testing

• Locally testing change files
• make test
• E2E testing

New tests cover the changes: yes

Description for the changelog

Enhancement: Migrate jsonutil to encoding/json for aws-sdk-go-v2 migration

Licensing

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.