Add lambda-s3-download pattern for streaming URL downloads to S3

[roblOnTour]

Issue #, if available:
N/A

Description of changes:

New pattern: lambda-s3-download

A Lambda function (Python 3.12) that downloads a file from a URL and uploads it to S3 using multipart upload with SHA256 checksums. The file is streamed in configurable chunks through /tmp, allowing it to handle files larger than Lambda's memory limit.

Features:

• Chunked streaming download with configurable chunk size (clamped between 5 MB and 5 GB)
• S3 multipart upload with SHA256 checksum verification
• Automatic cleanup of incomplete multipart uploads on failure
• 15-minute timeout, 1 GB memory, 10 GB ephemeral storage

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