[batch] [request]: support mixed architectures in AWS Batch job queues

### Community Note

* Please vote on this issue by adding a 👍 [reaction](https://blog.github.com/2016-03-10-add-reactions-to-pull-requests-issues-and-comments/) to the original issue to help the community and maintainers prioritize this request
* Please do not leave "+1" or "me too" comments, they generate extra noise for issue followers and do not help prioritize the request
* If you are interested in working on this issue or have submitted a pull request, please leave a comment

**Tell us about your request**
We wish to submit batch jobs which support multiple architectures (arm64/amd64) to take advantage of spot pricing across a wider range of instance types

**Which service(s) is this request for?**
Batch

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
Currently AWS batch supports both amd64 and arm64 instance types, in distinct compute environments.
However, it's not possible to mix compute environment architectures in a single job queue.

We wish to take advantage of AWS graviton instances (c6g, m6g, c7g etc), but don't wish to constrain the availablilty of spot instances to only graviton instances - for previous generation intel instances we can mix in 4th and 5th gen instances to fall back to if supply isn't there on the bleeding edge.

As such, we want to be able to submit to a queue backed by both types, if graviton is not available, we wish to fall back to intel.

**Are you currently working around this issue?**
Not using ARM instances

Review the AWS Batch request and its stated limitation: separate amd64 and arm64 compute environments cannot share one queue. Done means a job queue can use both architectures and fall back between Graviton and Intel capacity; no repository file or test is identified in the issue.

Written by the indexing model from the issue text.