fix(aws_applicationautoscaling): Add missing members to PredefinedMetric enum (#18978)

Five predefined metrics for autoscaling using target tracking metrics are supported by CloudFormation but missing from the CDK enum PredefinedMetric. Fixes #18969 

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

Author: StevenSmiley

Diff for: packages/@aws-cdk/aws-applicationautoscaling/lib/target-tracking-scaling-policy.ts

@@ -184,12 +184,31 @@ function renderCustomMetric(metric?: cloudwatch.IMetric): CfnScalingPolicy.Custo
  */
 export enum PredefinedMetric {
   /**
-   * DYNAMODB_READ_CAPACITY_UTILIZATIO
-   * @see https://docs.aws.amazon.com/autoscaling/application/APIReference/API_PredefinedMetricSpecification.html
+   * Average percentage of instances in an AppStream fleet that are being used.
+   */
+  APPSTREAM_AVERAGE_CAPACITY_UTILIZATION = 'AppStreamAverageCapacityUtilization',
+  /**
+   * Percentage of provisioned read capacity units utilized by a Keyspaces table.
+   */
+  CASSANDRA_READ_CAPACITY_UTILIZATION = 'CassandraReadCapacityUtilization',
+  /**
+   * Percentage of provisioned write capacity units utilized by a Keyspaces table.
+   */
+  CASSANDRA_WRITE_CAPACITY_UTILIZATION = 'CassandraWriteCapacityUtilization',
+  /**
+   * Percentage of provisioned inference units utilized by a Comprehend endpoint.
+   */
+  COMPREHEND_INFERENCE_UTILIZATION = 'ComprehendInferenceUtilization',
+  /**
+   * Average CPU Utilization of read replica instances in a Neptune DB cluster.
+   */
+  NEPTURE_READER_AVERAGE_CPU_UTILIZATION = 'NeptuneReaderAverageCPUUtilization',
+  /**
+   * Percentage of provisioned read capacity units consumed by a DynamoDB table.
    */
   DYNAMODB_READ_CAPACITY_UTILIZATION = 'DynamoDBReadCapacityUtilization',
   /**
-   * DYNAMODB_WRITE_CAPACITY_UTILIZATION
+   * Percentage of provisioned write capacity units consumed by a DynamoDB table.
    *
    * Suffix `dummy` is necessary due to jsii bug (https://github.com/aws/jsii/issues/2782).
    * Duplicate values will be dropped, so this suffix is added as a workaround.