Look at upgrading AWS RHEL 7.6 system

RHEL 7.6 is rather out of date now so [test-aws-rhel76-armv8-1](https://ci.adoptium.net/computer/test%2Daws%2Drhel76%2Darmv8%2D1/) should be updated. However it would be good to continue to have one machine to be able to test on the AWS aarch64 Graviton hardware. I would propose that we update/replace this machine with something newer. Maybe RHEL10 if available on AWS without incurring too much extra cost, or we could look at an Ubuntu/CentOS-Stream version.

(Also noting that we have a RHEL8 x64 system at AWS that may be worth consideringing updating/replacing/removing - there is [one outstanding issue](https://github.com/adoptium/infrastructure/issues/1829) in this repo about that machine

Start by reviewing the test-aws-rhel76-armv8-1 machine linked in the issue and the related issue #1829 for the RHEL 8 AWS system. Compare possible replacement operating systems and AWS availability or cost, then document a clear decision for retaining aarch64 Graviton coverage and the resulting machine maintenance work.

Written by the indexing model from the issue text.