feat(redshift-alpha): add support for RA3.large node type (#31637)

### Issue # (if applicable)

Closes #31634.

### Reason for this change

add support for RA3.large node type

### Description of changes

extended the NodeType enum in ClusterProps.nodeType to include RA3.large

### Description of how you validated changes

ran all tests

### 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: AsadBinImtiaz

packages/@aws-cdk/aws-redshift-alpha/README.md

@@ -700,6 +700,7 @@ as it's a fast operation and typically completes in minutes. Elastic resize is o
   * dc2.8xlarge
   * ds2.xlarge
   * ds2.8xlarge
+  * ra3.large
   * ra3.xlplus
   * ra3.4xlarge
   * ra3.16xlarge

packages/@aws-cdk/aws-redshift-alpha/lib/cluster.ts

@@ -49,6 +49,11 @@ export enum NodeType {
    */
   DC2_8XLARGE = 'dc2.8xlarge',
 
+  /**
+   * ra3.large
+   */
+  RA3_LARGE = 'ra3.large',
+
   /**
    * ra3.xlplus
    */

packages/@aws-cdk/aws-redshift-alpha/test/cluster.test.ts

@@ -734,7 +734,7 @@ describe('multi AZ cluster', () => {
         masterPassword: cdk.SecretValue.unsafePlainText('tooshort'),
       },
       vpc,
-      nodeType: NodeType.RA3_XLPLUS,
+      nodeType: NodeType.RA3_LARGE,
       multiAz: true,
     });
 
@@ -747,7 +747,7 @@ describe('multi AZ cluster', () => {
       AutomatedSnapshotRetentionPeriod: 1,
       Encrypted: true,
       NumberOfNodes: 2,
-      NodeType: 'ra3.xlplus',
+      NodeType: 'ra3.large',
       DBName: 'default_db',
       PubliclyAccessible: false,
       ClusterSubnetGroupName: { Ref: 'RedshiftSubnetsDFE70E0A' },