Allow small cpu requests for Synchrony container

[bianchi2]

Addresses #644

This PR makes it possible to set smaller cpu requests for Synchrony container. Since we use synchrony.resources.container.requests.cpu in -XX:ActiveProcessorCount in synchrony entrypoint script as a JVM flag, setting anything less than 1 is n't possible since ActiveProcessorCount accepts int only. See: https://eclipse.dev/openj9/docs/xxactiveprocessorcount/. As a result, setting synchrony.resources.container.requests.cpu=100m or synchrony.resources.container.requests.cpu=0.5 results in Synchrony container crashing.

This PR adds a simple check - if synchrony.resources.container.requests.cpu contains m character, -XX:ActiveProcessorCount is set to 1.

I have also added a few comments to values.yaml docs, with a link to https://kubernetes.io/docs/concepts/configuration/manage-resources-containers/#meaning-of-cpu

2 simple unit tests check if -XX:ActiveProcessorCount=1 when synchrony.resources.container.requests.cpu=20m, and
if if -XX:ActiveProcessorCount=5 when synchrony.resources.container.requests.cpu=5

Also, Synchrony is enabled in KinD tests, which wasn't possible because it wasn't possible to have a small cpu claim (GitHub actions have limits)

Checklist

• I have added unit tests
• The E2E test has passed (use e2e label)

[bianchi2]

This will alow schedule synchrony pod, and ActiveProcessorCount will be set to 1.

[yzha645]

🚀