ci: Move kTLS test out of GeneralBatch

[dougch]

Release Summary:

Resolved issues:

n/a

Description of changes:

Replaces #4886. CodeBuild now supports ec2 instance types, move kTLS out of general batch and onto this new setup. Example run: here

Because this new CodeBuild feature does not support batch builds, I've added the kTLS ASAN job to the new kTLS buildspec serially. On the 8vcpu instance, total runtime is ~8 minutes, end to end.

Call-outs:

This moves us away from hand rolled QEMU VM images and onto a vended AL2023 AMI.

This change also directly uses the Nix s3 cache to speed up builds.

Release steps:

• While this is in review, I'll finalize the CodeBuild job
• Just prior to merging, the webhook will be turned on in "not required" mode.
• After some soak time, we'll mark it required

Testing:

How is this change tested (unit tests, fuzz tests, etc.)? On a new job called AMI Tester, see the linked run above
How can you convince your reviewers that this PR is safe and effective? ad-hoc test run, you can duplicate in AMI tester
Is this a refactor change? of s2n code, no, of CI, yes. No more Qemu or AL2 qcow images.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[dougch]

To confirm this change catches leaks, I ran this PR, with this patch applied and confirmed the new CodeBuild job fails.