fix: add proxy support for AWS SDK v3

[pru55e11]

This fixes the proxy bypass issue that occurred after the migration from AWS SDK v2 to v3 in March 2023.

PROBLEM:

• AWS SDK v3 requires different proxy configuration than v2
• Adobe I/O CLI S3 uploads were bypassing corporate proxies
• ECONNRESET errors in corporate environments

Inspired-by: PR #224 by pat-lego
Fixes: proxy bypass for Adobe I/O CLI S3 operations

SOLUTION:

• Add NodeHttpHandler with ProxyAgent for AWS SDK v3 compatibility
• Support standard proxy environment variables (https_proxy, HTTPS_PROXY, http_proxy, HTTP_PROXY)
• Maintain CommonJS compatibility (fixes ES6 import issues from PR Update remote-storage.js #224)
• Priority: HTTPS_PROXY > HTTP_PROXY (HTTPS takes precedence for S3)
• Only configure requestHandler when proxy is actually set

Tests

• Tested locally with linked library and observed traffic via MITM proxy.
• Comprehensive proxy configuration tests for all environment variables
• Proxy priority testing (HTTPS takes precedence)
• No-proxy scenario testing

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[shazron]

There's also the AWS https://github.com/awslabs/aws-sdk-v3-js-proxy but there is one issue from a dev that says it doesn't work - the approach in the PR is what is recommended