Tag AMI's with ena_support

[cartermckinnon]

Description of changes:

Enables ENA by default on instances launched with the AMIs. We already have the ena kernel module installed, and the base Amazon Linux AMIs have this enabled -- we just haven't been propagating the attribute to our AMI's.

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[cartermckinnon]

/ci

[github-actions[bot]]

@cartermckinnon roger that! I've dispatched a workflow. 👍

[github-actions[bot]]

@cartermckinnon the workflow that you requested has completed. 🎉

AMI variant	Build	Test
1.21 / al2	success ✅	success ✅
1.22 / al2	success ✅	success ✅
1.23 / al2	success ✅	success ✅
1.23 / al2023	success ✅	failure ❌
1.24 / al2	success ✅	success ✅
1.24 / al2023	success ✅	success ✅
1.25 / al2	success ✅	success ✅
1.25 / al2023	success ✅	success ✅
1.26 / al2	success ✅	success ✅
1.26 / al2023	success ✅	success ✅
1.27 / al2	success ✅	success ✅
1.27 / al2023	success ✅	success ✅
1.28 / al2	success ✅	success ✅
1.28 / al2023	success ✅	success ✅
1.29 / al2	success ✅	success ✅
1.29 / al2023	success ✅	success ✅
1.30 / al2	success ✅	success ✅
1.30 / al2023	success ✅	success ✅

[cartermckinnon]

This isn't actually needed, our AMI's already inherit this property. You just need to launch a Nitro instance and things work as expected.