chore(rds): supports Aurora PostgreSQL 16.4, 15.8, 14.13, 13.16, and …

…12.20 (#31604)

Add new cluster engines.

Ref: [Amazon Aurora supports PostgreSQL 16.4, 15.8, 14.13, 13.16, and 12.20](https://aws.amazon.com/about-aws/whats-new/2024/09/amazon-aurora-supports-postgresql-new-versions/)

### 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*

packages/aws-cdk-lib/aws-rds/lib/cluster-engine.ts

@@ -962,6 +962,8 @@ export class AuroraPostgresEngineVersion {
   public static readonly VER_12_18 = AuroraPostgresEngineVersion.of('12.18', '12', { s3Import: true, s3Export: true });
   /** Version "12.19". */
   public static readonly VER_12_19 = AuroraPostgresEngineVersion.of('12.19', '12', { s3Import: true, s3Export: true });
+  /** Version "12.20". */
+  public static readonly VER_12_20 = AuroraPostgresEngineVersion.of('12.20', '12', { s3Import: true, s3Export: true });
   /**
    *  Version "13.3".
    * @deprecated Version 13.3 is no longer supported by Amazon RDS.
@@ -1000,6 +1002,8 @@ export class AuroraPostgresEngineVersion {
   public static readonly VER_13_14 = AuroraPostgresEngineVersion.of('13.14', '13', { s3Import: true, s3Export: true });
   /** Version "13.15". */
   public static readonly VER_13_15 = AuroraPostgresEngineVersion.of('13.15', '13', { s3Import: true, s3Export: true });
+  /** Version "13.16". */
+  public static readonly VER_13_16 = AuroraPostgresEngineVersion.of('13.16', '13', { s3Import: true, s3Export: true });
   /** Version "14.3". */
   public static readonly VER_14_3 = AuroraPostgresEngineVersion.of('14.3', '14', { s3Import: true, s3Export: true });
   /**  Version "14.4". */
@@ -1020,6 +1024,8 @@ export class AuroraPostgresEngineVersion {
   public static readonly VER_14_11 = AuroraPostgresEngineVersion.of('14.11', '14', { s3Import: true, s3Export: true });
   /** Version "14.12". */
   public static readonly VER_14_12 = AuroraPostgresEngineVersion.of('14.12', '14', { s3Import: true, s3Export: true });
+  /** Version "14.13". */
+  public static readonly VER_14_13 = AuroraPostgresEngineVersion.of('14.13', '14', { s3Import: true, s3Export: true });
   /** Version "15.2". */
   public static readonly VER_15_2 = AuroraPostgresEngineVersion.of('15.2', '15', { s3Import: true, s3Export: true });
   /** Version "15.3". */
@@ -1032,6 +1038,8 @@ export class AuroraPostgresEngineVersion {
   public static readonly VER_15_6 = AuroraPostgresEngineVersion.of('15.6', '15', { s3Import: true, s3Export: true });
   /** Version "15.7". */
   public static readonly VER_15_7 = AuroraPostgresEngineVersion.of('15.7', '15', { s3Import: true, s3Export: true });
+  /** Version "15.8". */
+  public static readonly VER_15_8 = AuroraPostgresEngineVersion.of('15.8', '15', { s3Import: true, s3Export: true });
   /**
    * Version "16.0"
    * @deprecated Version 16.0 is no longer supported by Amazon RDS.
@@ -1043,6 +1051,8 @@ export class AuroraPostgresEngineVersion {
   public static readonly VER_16_2 = AuroraPostgresEngineVersion.of('16.2', '16', { s3Import: true, s3Export: true });
   /** Version "16.3". */
   public static readonly VER_16_3 = AuroraPostgresEngineVersion.of('16.3', '16', { s3Import: true, s3Export: true });
+  /** Version "16.4". */
+  public static readonly VER_16_4 = AuroraPostgresEngineVersion.of('16.4', '16', { s3Import: true, s3Export: true });
 
   /**
    * Create a new AuroraPostgresEngineVersion with an arbitrary version.