feat(appconfig): constrain environments to a single deployment at a time (#29500)

### Issue # (if applicable)

Closes #29345.

### Reason for this change

The current L2 AppConfig constructs do not have any guardrails 
that prevent simultaneous Deployments to a single Environment. 
This is not allowed, and will result in Cfn deploy-time conflicts.

### Description of changes

This commit adds a pair of new public methods to IEnvironment that 
enable the addition of a new Deployment for a given IConfiguration.

It then updates the creation of new Deployments in ConfigurationBase 
to utilize these new methods instead of the current resource creation.

These new methods interact with an internal queue. 
This queue creates a chain of Cfn dependencies between Deployments 
in order to enforce that only a single Deployment can be in progress 
for the Environment at any given time.

### Description of how you validated changes

Added new unit and integ test coverage.  
Deployed the new integ test without these changes and confirmed that Cfn failed at deployment time. 

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

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

Author: M-Hawkins

packages/@aws-cdk-testing/framework-integ/test/aws-appconfig/test/integ.multi-config-env.js.snapshot/appconfigmulticonfigenvDefaultTestDeployAssert1621E45D.assets.json

@@ -0,0 +1,156 @@
+{
+ "Resources": {
+  "MyApplicationForEnv1F597ED9": {
+   "Type": "AWS::AppConfig::Application",
+   "Properties": {
+    "Name": "awsappconfigmulticonfigenv-MyApplicationForEnv-1EE3EA95"
+   }
+  },
+  "MultiConfigEnvironment5F41B747": {
+   "Type": "AWS::AppConfig::Environment",
+   "Properties": {
+    "ApplicationId": {
+     "Ref": "MyApplicationForEnv1F597ED9"
+    },
+    "Name": "awsappconfigmulticonfigenv-MultiConfigEnvironment-59525230"
+   }
+  },
+  "QuickDeploymentStrategy980252EC": {
+   "Type": "AWS::AppConfig::DeploymentStrategy",
+   "Properties": {
+    "DeploymentDurationInMinutes": 1,
+    "GrowthFactor": 50,
+    "GrowthType": "LINEAR",
+    "Name": "awsappconfigmulticonfigenv-QuickDeploymentStrategy-CAB72574",
+    "ReplicateTo": "NONE"
+   }
+  },
+  "MyFirstConfigConfigurationProfileAB11F87A": {
+   "Type": "AWS::AppConfig::ConfigurationProfile",
+   "Properties": {
+    "ApplicationId": {
+     "Ref": "MyApplicationForEnv1F597ED9"
+    },
+    "LocationUri": "hosted",
+    "Name": "awsappconfigmulticonfigenv-MyFirstConfig-2FF7CAAB"
+   }
+  },
+  "MyFirstConfig117AFBAC": {
+   "Type": "AWS::AppConfig::HostedConfigurationVersion",
+   "Properties": {
+    "ApplicationId": {
+     "Ref": "MyApplicationForEnv1F597ED9"
+    },
+    "ConfigurationProfileId": {
+     "Ref": "MyFirstConfigConfigurationProfileAB11F87A"
+    },
+    "Content": "first config content",
+    "ContentType": "application/octet-stream"
+   },
+   "UpdateReplacePolicy": "Retain",
+   "DeletionPolicy": "Retain"
+  },
+  "MyFirstConfigDeployment5AEBAD52B8EE4": {
+   "Type": "AWS::AppConfig::Deployment",
+   "Properties": {
+    "ApplicationId": {
+     "Ref": "MyApplicationForEnv1F597ED9"
+    },
+    "ConfigurationProfileId": {
+     "Ref": "MyFirstConfigConfigurationProfileAB11F87A"
+    },
+    "ConfigurationVersion": {
+     "Ref": "MyFirstConfig117AFBAC"
+    },
+    "DeploymentStrategyId": {
+     "Ref": "QuickDeploymentStrategy980252EC"
+    },
+    "EnvironmentId": {
+     "Ref": "MultiConfigEnvironment5F41B747"
+    }
+   }
+  },
+  "MySecondConfigConfigurationProfileD0CC1BAA": {
+   "Type": "AWS::AppConfig::ConfigurationProfile",
+   "Properties": {
+    "ApplicationId": {
+     "Ref": "MyApplicationForEnv1F597ED9"
+    },
+    "LocationUri": "hosted",
+    "Name": "awsappconfigmulticonfigenv-MySecondConfig-4F837809"
+   }
+  },
+  "MySecondConfig28DEBAC4": {
+   "Type": "AWS::AppConfig::HostedConfigurationVersion",
+   "Properties": {
+    "ApplicationId": {
+     "Ref": "MyApplicationForEnv1F597ED9"
+    },
+    "ConfigurationProfileId": {
+     "Ref": "MySecondConfigConfigurationProfileD0CC1BAA"
+    },
+    "Content": "second config content",
+    "ContentType": "application/octet-stream"
+   },
+   "UpdateReplacePolicy": "Retain",
+   "DeletionPolicy": "Retain"
+  },
+  "MySecondConfigDeployment5AEBAD1470BE4": {
+   "Type": "AWS::AppConfig::Deployment",
+   "Properties": {
+    "ApplicationId": {
+     "Ref": "MyApplicationForEnv1F597ED9"
+    },
+    "ConfigurationProfileId": {
+     "Ref": "MySecondConfigConfigurationProfileD0CC1BAA"
+    },
+    "ConfigurationVersion": {
+     "Ref": "MySecondConfig28DEBAC4"
+    },
+    "DeploymentStrategyId": {
+     "Ref": "QuickDeploymentStrategy980252EC"
+    },
+    "EnvironmentId": {
+     "Ref": "MultiConfigEnvironment5F41B747"
+    }
+   },
+   "DependsOn": [
+    "MyFirstConfigDeployment5AEBAD52B8EE4"
+   ]
+  }
+ },
+ "Parameters": {
+  "BootstrapVersion": {
+   "Type": "AWS::SSM::Parameter::Value<String>",
+   "Default": "/cdk-bootstrap/hnb659fds/version",
+   "Description": "Version of the CDK Bootstrap resources in this environment, automatically retrieved from SSM Parameter Store. [cdk:skip]"
+  }
+ },
+ "Rules": {
+  "CheckBootstrapVersion": {
+   "Assertions": [
+    {
+     "Assert": {
+      "Fn::Not": [
+       {
+        "Fn::Contains": [
+         [
+          "1",
+          "2",
+          "3",
+          "4",
+          "5"
+         ],
+         {
+          "Ref": "BootstrapVersion"
+         }
+        ]
+       }
+      ]
+     },
+     "AssertDescription": "CDK bootstrap stack version 6 required. Please run 'cdk bootstrap' with a recent version of the CDK CLI."
+    }
+   ]
+  }
+ }
+}