Use hidden parameter plugin to hide docker and aws parameters from users

[cliffano]

We need to hide a number of parameters which are set up once-off during pipeline provisioning. The idea is that we shouldn't confuse users (specially non-ops folks) when they see the build parameters list, some of those parameters don't need to be modified during on-demand execution of the build pipelines.

The ones that need to be hidden are:

• JENKINS_AGENT_DOCKER_IMAGE
• JENKINS_AGENT_DOCKER_ARGS
• AWS_LIBRARY_S3_BUCKET
• AWS_LIBRARY_S3_PATH