Add ability to provide module with cert ARN & Other Fixes

[jamesstonehill]

When attempting to deploy langfuse, we encountered a few issues. This PR fixes some of these issues. The changes made are:

• Ability to pass in pre-created certificate: It's nice to be able to pass in a pre-existing certificate so that if you have a wildcard certificate like *.example.com you can use this certificate for your langfuse deployment on langfuse.example.com.
• Ability to skip dns setup. The current DNS setup assumes AWS is your registrar. We use Cloudflare so the current setup wouldn't work for us so this PR adds the ability to skip the DNS setup and exposes the k8s lb needed to setup DNS externally.
• Unique IAM names. Currently the IAM resources uses just the name property. This means that if you wanted to have two langfuse deployments in the same AWS account (e.g. with a mult-regional setup), you'd end up getting IAM role name clashes. This PR changes it so that the IAM resources now use name_prefix to avoid name clashes. [THIS IS A BREAKING CHANGE] because it requires some resources to be recreated so should only be released as part of a major release.
• Adds kubernetes_annotations needed for CoreDNS.

[CLAassistant]

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