provider/aws: Allow empty S3 config in Cloudfront Origin

[catsby]

If both custom and s3 origin are missing, add an empty s3 origin... one or the other must be specified, but the S3 origin can be "empty". Fixes #6422

[catsby]

Waiting on acc tests (which take some time) to complete, will update when they do!

[phinze]

Code LGTM 👍

[catsby]

Tests pass

==> Checking that code complies with gofmt requirements...
/Users/clint/Projects/Go/bin/stringer
go generate $(go list ./... | grep -v /vendor/)
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSCloudFrontDistribution_ -timeout 120m
=== RUN   TestAccAWSCloudFrontDistribution_S3Origin
--- PASS: TestAccAWSCloudFrontDistribution_S3Origin (21.72s)
=== RUN   TestAccAWSCloudFrontDistribution_customOrigin
--- PASS: TestAccAWSCloudFrontDistribution_customOrigin (9.36s)
=== RUN   TestAccAWSCloudFrontDistribution_multiOrigin
--- PASS: TestAccAWSCloudFrontDistribution_multiOrigin (19.68s)
=== RUN   TestAccAWSCloudFrontDistribution_noOptionalItemsConfig
--- PASS: TestAccAWSCloudFrontDistribution_noOptionalItemsConfig (8.15s)
=== RUN   TestAccAWSCloudFrontDistribution_noCustomErrorResponseConfig
--- PASS: TestAccAWSCloudFrontDistribution_noCustomErrorResponseConfig (7.03s)
PASS
ok      github.com/hashicorp/terraform/builtin/providers/aws    65.963s

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.