refactor: clean up API for removal policy across the library (#2893)

- Normalize how deletion policy is configured for stateful resources across the AWS Construct Library. - Simplify the model by removing the future-proofing of "RemovalPolicy.Forbid".
- When `RemovalPolicy.Destory` is used, explicitly specify `DeletionPolicy: Delete` in CloudFormation (as oppose to relying on the fact the "Delete" is the default).

BREAKING CHANGE: multiple modules have been changed to use `cdk.RemovalPolicy`
to configure the resource's removal policy.
* **core:** `applyRemovalPolicy` is now `CfnResource.applyRemovalPolicy`.
* **core:** `RemovalPolicy.Orphan` has been renamed to `Retain`.
* **core:** `RemovalPolicy.Forbid` has been removed, use `Retain`.
* **ecr:** `RepositoryProps.retain` is now `removalPolicy`, and defaults to `Retain` instead of remove since ECR is a stateful resource
* **kms:** `KeyProps.retain` is now `removalPolicy`
* **logs:** `LogGroupProps.retainLogGroup` is now `removalPolicy`
* **logs:** `LogStreamProps.retainLogStream` is now `removalPolicy`
* **rds:** `DatabaseClusterProps.deleteReplacePolicy` is now `removalPolicy`
* **rds:** `DatabaseInstanceNewProps.deleteReplacePolicy` is now `removalPolicy`

Author: Elad Ben-Israel

packages/@aws-cdk/app-delivery/test/integ.cicd.expected.json

@@ -1,6 +1,7 @@
 {
   "Resources": {
     "ArtifactBucket7410C9EF": {
+      "DeletionPolicy": "Delete",
       "Type": "AWS::S3::Bucket"
     },
     "CodePipelineRoleB3A660B4": {
@@ -281,4 +282,4 @@
       }
     }
   }
-}
+}

packages/@aws-cdk/aws-cloudfront/test/integ.cloudfront-bucket-logging.expected.json

@@ -1,6 +1,7 @@
 {
   "Resources": {
     "Bucket83908E77": {
+      "DeletionPolicy": "Delete",
       "Type": "AWS::S3::Bucket"
     },
     "AnAmazingWebsiteProbablyCFDistribution47E3983B": {

packages/@aws-cdk/aws-cloudfront/test/integ.cloudfront-ipv6-disabled.expected.json

@@ -1,6 +1,7 @@
 {
   "Resources": {
     "Bucket83908E77": {
+      "DeletionPolicy": "Delete",
       "Type": "AWS::S3::Bucket"
     },
     "MyDistributionCFDistributionDE147309": {

packages/@aws-cdk/aws-cloudfront/test/integ.cloudfront-lambda-association.expected.json

@@ -1,6 +1,7 @@
 {
   "Resources": {
     "Bucket83908E77": {
+      "DeletionPolicy": "Delete",
       "Type": "AWS::S3::Bucket"
     },
     "LambdaServiceRoleA8ED4D3B": {

packages/@aws-cdk/aws-cloudfront/test/integ.cloudfront-s3.expected.json

@@ -1,6 +1,7 @@
 {
   "Resources": {
     "Bucket83908E77": {
+      "DeletionPolicy": "Delete",
       "Type": "AWS::S3::Bucket"
     },
     "BucketPolicyE9A3008A": {

packages/@aws-cdk/aws-cloudfront/test/integ.cloudfront.expected.json

@@ -1,6 +1,7 @@
 {
   "Resources": {
     "Bucket83908E77": {
+      "DeletionPolicy": "Delete",
       "Type": "AWS::S3::Bucket"
     },
     "MyDistributionCFDistributionDE147309": {

packages/@aws-cdk/aws-cloudtrail/test/integ.cloudtrail.lit.expected.json

@@ -1,7 +1,8 @@
 {
   "Resources": {
     "Bucket83908E77": {
-      "Type": "AWS::S3::Bucket"
+      "Type": "AWS::S3::Bucket",
+      "DeletionPolicy": "Delete"
     },
     "TrailS30071F172": {
       "Type": "AWS::S3::Bucket",
@@ -124,4 +125,4 @@
       ]
     }
   }
-}
+}

packages/@aws-cdk/aws-codebuild/test/integ.caching.expected.json

@@ -1,6 +1,7 @@
 {
   "Resources": {
     "CacheBucket41D9D0B0": {
+      "DeletionPolicy": "Delete",
       "Type": "AWS::S3::Bucket"
     },
     "MyProjectRole9BBE5233": {

packages/@aws-cdk/aws-codebuild/test/integ.ecr.lit.expected.json

@@ -1,6 +1,7 @@
 {
   "Resources": {
     "MyRepoF4F48043": {
+      "DeletionPolicy": "Retain",
       "Type": "AWS::ECR::Repository",
       "Properties": {
         "RepositoryPolicyText": {

packages/@aws-cdk/aws-codebuild/test/integ.project-bucket.expected.json

@@ -1,6 +1,7 @@
 {
   "Resources": {
     "MyBucketF68F3FF0": {
+      "DeletionPolicy": "Delete",
       "Type": "AWS::S3::Bucket"
     },
     "MyProjectRole9BBE5233": {