feat(cloudwatch): support composite alarm lifecycle (#6408)

(cherry picked from commit 922e36a472341861e97d1b5639656f3c4a3978d8)

docs/services/cloudformation.md

@@ -160,7 +160,7 @@ cross-resource references.
 | Kinesis Data Firehose | `DeliveryStream` |
 | IoT Core | `DomainConfiguration` (`ServerCertificates` resolves to a JSON string), `Policy` (deleted after detaching it from its principals; on AWS the delete fails with `DeleteConflictException` while the policy is attached), `Thing`, `TopicRule` |
 | CloudFront | `CachePolicy`, `Distribution`, `OriginAccessControl`, `OriginRequestPolicy`, `ResponseHeadersPolicy` |
-| CloudWatch | `Alarm`, `Dashboard` |
+| CloudWatch | `Alarm`, `CompositeAlarm`, `Dashboard`. Composite alarms have backing definitions with name Ref and Arn GetAtt, rollback, and replacement cleanup. Composite actions are stored only; suppression properties are rejected. |
 | CloudWatch Logs | `LogGroup`, `LogStream`, `MetricFilter` |
 | WAFv2 | `WebACL` |
 | Config | `ConfigRule` |

docs/services/cloudwatch.md

@@ -311,6 +311,7 @@ aws logs put-retention-policy \
 | `GetMetricStatistics` | Get metric statistics (Average, Sum, etc.) |
 | `GetMetricData` | Query metrics with math expressions |
 | `PutMetricAlarm` | Create a metric alarm |
+| `PutCompositeAlarm` | Create or update a composite alarm rule |
 | `DescribeAlarms` | List alarms |
 | `DeleteAlarms` | Delete alarms |
 | `SetAlarmState` | Manually set alarm state |
@@ -331,6 +332,11 @@ aws logs put-retention-policy \
 Metric streams are stored as definitions with their `running` or `stopped` state. Floci never
 delivers metrics to the Firehose delivery stream a metric stream names.
 
+Composite alarms support boolean rules over alarm states. Request `AlarmTypes` containing
+`CompositeAlarm` when describing them; the default describes metric alarms. Composite
+action lists are stored but not executed. Action suppression is not implemented and is
+rejected with `ValidationError`.
+
 ### SNS alarm actions
 
 State transitions publish to same-account standard SNS topics in `AlarmActions`, `OKActions`, or