Update base ec2 test framework

[andrewhop]

Description of changes:

1. Use latest ARM Ubuntu image
2. Tag instances with a name that links back to the requesting PR to make tracking leaks easier
3. Add a final log message to see if that shows up in CloudWatch logs

Call-outs:

I think the older AMI just happened to have an SSM agent that couldn't handle the large output of the single "command" and crashed with document process failed unexpectedly: document worker timed out I haven't been able to reproduce that issue with this newer AMI.

Verified in the ec2 console the new name shows up {Key="Name",Value="ec2-test-pr/1395"}

Testing:

Manually tested with SSM run command in my account, lets see what happens here.

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

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e6e201b) 76.81% compared to head (c36e5bf) 76.80%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1395      +/-   ##
==========================================
- Coverage   76.81%   76.80%   -0.01%     
==========================================
  Files         424      424              
  Lines       71338    71338              
==========================================
- Hits        54798    54793       -5     
- Misses      16540    16545       +5     

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