Use environment variables for workflow inputs

[zhihonl]

Description of the issue

The GitHub Actions workflows use inconsistent patterns for handling workflow inputs. Some workflows directly interpolate ${{ inputs.* }} values in shell commands, while others use the recommended env: block pattern. This inconsistency makes the codebase harder to maintain and doesn't follow GitHub Actions best practices.

Description of changes

Standardized input handling across 9 workflow files to use the env: block pattern:

Workflow File	Changes
test-artifacts.yml	Moved inputs.test_repo_branch and inputs.build_id to env variables
integration-test.yml	Moved inputs.build_sha to env variable
application-signals-e2e-test.yml	Moved inputs.build_sha to env variable
release-candidate-test.yml	Moved inputs.test_repo_branch to env variable
repackage-release-artifacts.yml	Moved inputs.build_id to env variable across 4 steps
upload-dependencies.yml	Moved inputs.s3_integration_bucket and inputs.github_sha to env variables
eks-performance-cluster-addon-install.yml	Moved multiple inputs to env variables in helm and git clone steps
wd-integration-test.yml	Moved inputs.build_sha to env variable
test-build.yml	Moved inputs.Bucket and inputs.BucketKey to env variables

The pattern change:

# Before
- run: |
    echo "${{ inputs.value }}"

# After  
- env:
    VALUE: ${{ inputs.value }}
  run: |
    echo "$VALUE"

License

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Tests

1. https://github.com/aws/amazon-cloudwatch-agent/actions/runs/20602789874
2. https://github.com/aws/amazon-cloudwatch-agent/actions/runs/20603161281
3. https://github.com/aws/amazon-cloudwatch-agent/actions/runs/20603161294
4. https://github.com/aws/amazon-cloudwatch-agent/actions/runs/20603162022
5. https://github.com/aws/amazon-cloudwatch-agent/actions/runs/20603161535

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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