Skip distributor re-build

[jefchien]

Description of the issue

Follow up for #1905. The scheduled build-test-artifacts runs are currently failing as it is trying to recreate/reupload the same distributor version (https://github.com/aws/amazon-cloudwatch-agent/actions/runs/18681788464/job/53265103408)

Description of changes

• Add check to skip distributor build if already done.
• Add step to delete oldest version if limit is reached.

License

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

Tests

• Skips distributor re-build: https://github.com/aws/amazon-cloudwatch-agent/actions/runs/18664691046/job/53217251141
• Checks the version limit: https://github.com/aws/amazon-cloudwatch-agent/actions/runs/18664691046/job/53214567908

Requirements

Before commiting your code, please do the following steps.

1. Run make fmt and make fmt-sh
2. Run make lint

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Integration Tests

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