feat(cli-integ): speed up image pulls by logging into ECR public

[iliapolo]

When running the suite on CodeBuild, we are seeing timeout failures in the following tests:

• CDK synth add the metadata properties expected by sam
• CDK synth bundled functions as expected
• test resource import with construct that requires bundling
• deploy new style synthesis to new style bootstrap (with docker image)
• all calls from isolated container go through proxy

These are all tests that either directly pull from public.ecr.gallery, or do so as part of cdk synth. In both cases, the pull is unauthenticated, and is therefore susceptible to stricter throttling limits, which can significantly slow things down.

Running the tests individually succeeds, so it must be something to do with the high concurrency introduced by atmosphere.
Lets login to ECR public before every test. I'm not convinced this will solve the issue, but it can't hurt and worst case we eliminate that as a cause and continue investigating.

Why are we not seeing the same errors when running in GitHub?

My theory right now is that CodeBuild IP addresses are being throttled much more aggressively than Github ones.