Add Azure Container Instances infrastructure block

[rpeden]

Summary

This PR adds an Azure Container Instances infrastructure block. The block provides a serverless infrastructure option on Azure similar to ECSTask on AWS and CloudRunJob on GCP.

Working

• Flow runs on Azure Container Instances
• Service Principal authentication
• Adjustable memory, CPU, and GPU resources
• Private container registries
• Subnets
• Output streaming

Steps to QA

• Have an Azure account with an active subscription, or set one up. Then, on Azure:
  • Create a service principal account
  • Create a resource group
• Run Prefect Orion
• Add an Azure Container Credentials block document using your service principal credentials
• Add an Azure Container Instances infrastructure block. Select the credentials you just created, then enter your resource group name and subscription ID, and set any other settings where you want to test non-default values
• Create and apply a deployment that uses your infrastructure block.
• Run a flow for the deployment.

QA Done

• 100+ manual flow runs on Azure Container Instances using both Prefect Orion and Prefect Cloud
• Created scheduled flows and ensured they run and finish reliably without errors
• Manual testing assistance from @prefectcboyd

Relevant Issue(s)

Closes #44

Checklist

• This pull request references any related issue by including "closes <link to issue>"
• This pull request includes tests or only affects documentation.
• This pull request includes a fix, feature, enhancement, docs, collections, or maintenance label categorizing the change.

[ahuang11]

This looks really good, thanks so much for taking this on! Left a few comments and suggestions.

Also, once you start adding tests, can you also add example usage at the top of the module?
Really appreciate this!

[rpeden]

Everything worked during manual testing with all the latest changes incorporated. The README examples needed minor changes but they now work as expected.

I'll also have a longer tutorial ready to publish when we merge and release this so any user that wants to try this infra block will have an end-to-end guide that walks them through it.

[desertaxle]

This is looking great! I have a couple of requests/suggestions related to code organization and naming. If you have any questions about any of my notes feel free to reach out!

[ahuang11]

Thanks for all the revisions! If a test run works with all the latest revisions, I think we can merge and make a prefect-azure release.

[rpeden]

Thanks for all the revisions! If a test run works with all the latest revisions, I think we can merge and make a prefect-azure release.

No problem! It's been a pleasure working on this, and I appreciate all the helpful feedback and assistance.

[rpeden]

Following up re: testing, I did another round of manual testis with the latest changes and all my container instance flows ran successfully.

:P