feat(toolkit-lib): support CloudFormation rollback triggers

[mattmb-aws]

Expose CloudFormation rollback triggers (rollback alarms + monitoring time) so a stack create/update is automatically rolled back when a CloudWatch alarm breaches.

• toolkit-lib: new public rollbackConfiguration deploy option (RollbackConfiguration/RollbackTrigger/RollbackTriggerType). It is validated (<=5 triggers, valid alarm ARNs, 0-180 min) and threaded through to the Create/Update/CreateChangeSet calls, with change detection so an unchanged config does not force a deployment.
• cli: new cdk deploy --rollback-trigger-alarm-arns and --monitoring-time-minutes flags. CLI ARNs default to metric alarms; composite alarms are reachable via the programmatic API.

Follows the same undefined/[]/[...] management semantics as notificationArns.

Fixes aws/aws-cdk#5170

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

Fixes #

Checklist

• This change contains a major version upgrade for a dependency and I confirm all breaking changes are addressed
  • Release notes for the new version:

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[codecov-commenter]

Codecov Report

❌ Patch coverage is 86.66667% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.08%. Comparing base (7ff50e7) to head (bd51232).

Files with missing lines	Patch %	Lines
packages/aws-cdk/lib/cli/cli.ts	60.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1881      +/-   ##
==========================================
- Coverage   91.10%   91.08%   -0.02%     
==========================================
  Files          80       80              
  Lines       12205    12233      +28     
  Branches     1742     1744       +2     
==========================================
+ Hits        11119    11143      +24     
- Misses       1050     1054       +4     
  Partials       36       36              

Flag	Coverage Δ
suite.unit	91.08% <86.66%> (-0.02%)	⬇️

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