Migrate `github.com/keptn/go-utils` to the same version as the datadog-service (or Keptn) version

[vadasambar]

Problem statement.
Right now we use an older version (0.15.0) of github.com/keptn/go-utils for datadog-service versions greater than 0.15.0. It'd be good to match the github.com/keptn/go-utils with the datadog-service version. go-utils matches Keptn versions i.e., if Keptn version is 0.15.0, go-utils version would (and should) be 0.15.0

Describe the solution you'd like
X version of datadog-service should use X version of go-utils. e.g.,
0.15.1 version of datadog-service should use 0.15.1 version of go-utils
0.16.1 version of datadog-service should use 0.16.1 version of go-utils

Describe alternatives you've considered
I don't think there are any alternatives here.

TODO

• Upgrade the version in go.mod for datadog-service versions > 0.15.1
• Raise a PR against release-0.15.1 (or any other datadog-service version you are working with)
• Run the e2e integration tests for your branch (go here and manually trigger integration tests for your branch as shown in the screenshot below)