Notable changes:
* backend/s3: Automatic validation of `eu-north-1` region
* backend/s3: Support for `credential_process` handling in AWS configuration file
Updated via:
```
go get github.com/aws/aws-sdk-go@v1.16.4
go get github.com/terraform-providers/terraform-provider-aws@v1.52.0
go mod tidy
go mod vendor
```
Here we upgrade the AWS Go SDK to 1.12.27 and AWS provider to include terraform-providers/terraform-provider-aws#1608.
This includes the capability to use named credentials profiles from the `~/.aws/credentials` file to authenticate to the backend.
* provider/aws: New resource codepipeline
* Vendor aws/codepipeline
* Add tests
* Add docs
* Bump codepipeline to v1.6.25
* Adjustments based on feedback
* Force new resource on ID change
* Improve tests
* Switch update to read
Since we don't require a second pass, only do a read.
* Skip tests if GITHUB_TOKEN is not set
Brian Flad