feat: Add support for aws_backup_region_settings resource

[lgallard]

New Argument Enhancement Request

Enhancement Details

Resource: aws_backup_plan
New Argument: opt_in_to_archive_for_supported_resources
Priority: medium

Description

This setting will instruct your backup plan to transition supported resources to archive (cold) storage tier in accordance with your lifecycle settings

Implementation Impact

Enables automatic archival for cost optimization

Auto-Discovery Metadata

• Discovered by: AWS Backup Feature Discovery Bot
• Scan Date: 2025-01-16T10:15:00Z
• Workflow Run: 19397556205

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Auto-generated by AWS Backup Feature Discovery Bot

[lgallard]

Resolved by #310 - AWS Backup region settings support has been implemented.

The merged PR adds:

• aws_backup_region_settings resource
• Configuration for resource type opt-in preferences
• Optional resource type management preferences
• Comprehensive example in examples/region_settings/
• Full documentation and validation

Additionally includes security, performance, and reliability improvements based on bug hunt analysis.