Delete obsolete AWS files

[jdmooney]

No description provided.

[vnandwana]

None of these docs are obsolete. We still offer and support CF, SingleTier, and MultiTier AMIs.
All the performance monitoring and error tracking tools, mentioned in the aws-tools.adoc, are also supported.

[reshmabidikar]

@jdmooney, does the below look correct?

• awf-cf.adoc replaced how-to-set-up-a-cloud-formation-system.adoc/how-to-maintain-a-cloud-formation-system.adoc
• aws-multitier.adoc replaced by how-to-set-up-a-multi-tier-system.adoc/how-to-maintain-a-multi-tier-system.adoc
• aws-single-ami.adoc//aws-singletier.adoc replaced by how-to-set-up-a-single-tier-system.adoc/how-to-maintain-a-single-tier-system.adoc
• aws-tools.adoc replaced by various docs like metrics_cloudwatch, etc.

I believe aws.adoc is not obsolete and needs to be retained, I see it referenced in our public docs: https://docs.killbill.io/latest/aws. If you agree, could you please add it back?

[jdmooney]

Will be replaced by new PR