`stacker.util.ensure_s3_bucket` function does not tag S3 buckets created

Currently S3 buckets created by stacker do not have any tags, even if that bucket is created on a stacker build run with a stacker config yaml defining tags. This is because the `ensure_s3_bucket` function imported by base and aws_lambda do not submit tags to the function.

We should probably tag the S3 buckets. My concern is not the buckets storing the json templates, but the buckets created for uploads of serverless lambda functions as they could get big and actually have somewhat of an effect on a budget.

So I propose the following...

- We modify the function to tag S3 buckets based on the `tags` top level keyword
- We create a new argument in the `aws_lambda.upload_lambda_functions` function to allow an override, in case an end-user wants to specify a different set of tags for the S3 bucket created by aws_lambda.py:493

I think this should cover all bases as to cost tags that may be required by businesses using stacker.