Add KMS effective-access evidence gates to aws-review

[KooZuKi]

Summary

• add a KMS effective-access review step for key policies, IAM delegation, and grants
• add service constraints, encryption context, CloudTrail, XKS, and multi-Region replica evidence gates
• add KMS report fields, severity guidance, references, and changelog entry

Validation

• git diff --check
• local frontmatter required-field check
• local prompt-injection pattern scan

Bounty

Addresses #1177. Preferred payment details can be provided privately after acceptance.