AWS China Support

[jbeemster]

This PR updates the AWS quickstart for both iglu_server and pipeline to work in the AWS China regions (cn-north-1) and (cn-northwest-1).

The main changes in the underlying modules are that:

1. IAM partitions now conditionally change to aws-cn if cn- is dedicated in the AWS Region and;
2. We offer Private ECR registry support for all modules now

The second one is important because when testing this DockerHub pulls pretty well always failed (and it is where we store our container images). To use these modules in AWS China you need to build your own ECR mirror in the same sub-account you intend to run the pipeline and manually upload the linux/amd64 platform images into ECR.

Once that is done set the private_ecr_registry variable to something like 000000000000.dkr.ecr.cn-north-1.amazonaws.com.cn/ (note: you need to maintain the trailing slash).

What loaders work?

Not all loaders work out of the box - specifically:

1. Snowflake RDB Loader does not work
2. Databricks RDB Loader does not work

All other loaders should work just fine!