AWS scraper: preserve required option markers

[thomhurst]

Problem

AwsCliScraper hard-codes every named option as optional, discarding AWS help required markers. Generated services therefore allow invalid empty calls such as EC2 terminate-instances without --instance-ids or create-key-pair without --key-name.

Acceptance criteria

• Capture required markers from AWS synopsis and option documentation.
• Generate required constructor members and non-null service facade parameters.
• Preserve compatibility only for shipped APIs.
• Add regression tests for EC2 terminate-instances and create-key-pair.
• Regenerate affected AWS options and facades.

Discovered while validating #4311.

[thomhurst]

Claimed for implementation. I will preserve AWS required-option markers through parsing/generation, add focused EC2 regressions, and regenerate only affected artifacts through the production generator.