chore(codebuild): add new CodeBuild lambda dotnet8 compute images (#30564)

Add new Lambda dotnet8 compute images for both aarch64 and x86_64 architectures:
- aws/codebuild/amazonlinux-aarch64-lambda-standard:dotnet8
- aws/codebuild/amazonlinux-x86_64-lambda-standard:dotnet8

**References**
- https://docs.aws.amazon.com/codebuild/latest/userguide/build-env-ref-available.html#lambda-compute-images
- #28630
- aws/aws-codebuild-docker-images#719

----

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

Author: RationalKuma4

packages/aws-cdk-lib/aws-codebuild/lib/linux-arm-lambda-build-image.ts

@@ -39,6 +39,8 @@ export class LinuxArmLambdaBuildImage implements IBuildImage {
   public static readonly AMAZON_LINUX_2_GO_1_21 = LinuxArmLambdaBuildImage.fromCodeBuildImageId('aws/codebuild/amazonlinux-aarch64-lambda-standard:go1.21');
   /** The `aws/codebuild/amazonlinux-aarch64-lambda-standard:dotnet6` build image. */
   public static readonly AMAZON_LINUX_2_DOTNET_6 = LinuxArmLambdaBuildImage.fromCodeBuildImageId('aws/codebuild/amazonlinux-aarch64-lambda-standard:dotnet6');
+  /** The `aws/codebuild/amazonlinux-aarch64-lambda-standard:dotnet8` build image. */
+  public static readonly AMAZON_LINUX_2023_DOTNET_8 = LinuxArmLambdaBuildImage.fromCodeBuildImageId('aws/codebuild/amazonlinux-aarch64-lambda-standard:dotnet8');
 
   /**
    * Uses a Docker image provided by CodeBuild.

packages/aws-cdk-lib/aws-codebuild/lib/linux-lambda-build-image.ts

@@ -39,6 +39,8 @@ export class LinuxLambdaBuildImage implements IBuildImage {
   public static readonly AMAZON_LINUX_2_GO_1_21 = LinuxLambdaBuildImage.fromCodeBuildImageId('aws/codebuild/amazonlinux-x86_64-lambda-standard:go1.21');
   /** The `aws/codebuild/amazonlinux-x86_64-lambda-standard:dotnet6` build image. */
   public static readonly AMAZON_LINUX_2_DOTNET_6 = LinuxLambdaBuildImage.fromCodeBuildImageId('aws/codebuild/amazonlinux-x86_64-lambda-standard:dotnet6');
+  /** The `aws/codebuild/amazonlinux-x86_64-lambda-standard:dotnet8` build image. */
+  public static readonly AMAZON_LINUX_2023_DOTNET_8 = LinuxLambdaBuildImage.fromCodeBuildImageId('aws/codebuild/amazonlinux-x86_64-lambda-standard:dotnet8');
 
   /**
    * Uses a Docker image provided by CodeBuild.