aws-codebuild: Can't use standard images on GPU instance

### Describe the bug

Creating codebuild project via console, I can create using standard images e.g. `aws/codebuild/standard:7.0`.
However, using CDK, in order to create a GPU project AFAICT I need to use LinuxGpuBuildImage - so I can only create using DLC images - see https://github.com/aws/aws-cdk/blob/main/packages/aws-cdk-lib/aws-codebuild/lib/linux-gpu-build-image.ts#L22 . Not only that, but the DLC images available as constants are 4 years old
Why not allow to create via image id here as well?

### Expected Behavior

Create GPU project using standard image, from image id, or from LinuxGpuBuildImage constant.
_Or_, have separate way to specify that the build uses GPU, regardless of BuildImage type (similar to console).

### Current Behavior

In order to use GPU, must use LinuxGpuBuildImage. Selection of LinuxGpuBuildImage is limited compared to console, and doesn't offer standard images.

### Reproduction Steps

LinuxGpuBuildImage.fromCodeBuildImageId - doesn't exist
LinuxGpuBuildImage.STANDARD_7_0 - doesn't exist
LinuxBuildImage.STANDARD_7_0 - no other way to specify to use GPU on this image

### Possible Solution

1. Add separate Project field specifying GPU-enabled build
2. Add ability to select Standard LinuxGpuBuildImage by image id

### Additional Information/Context

_No response_

### CDK CLI Version

2.127.0

### Framework Version

_No response_

### Node.js Version

18

### OS

AL2

### Language

TypeScript

### Language Version

_No response_

### Other information

_No response_

Start with packages/aws-cdk-lib/aws-codebuild/lib/linux-gpu-build-image.ts and compare the LinuxGpuBuildImage and LinuxBuildImage entry points named in the issue. Trace how the CDK project configuration represents GPU builds and determine whether image IDs or a separate GPU setting fits the existing API. Done means a GPU project can use the requested standard image path, with coverage for the supported configuration.

Written by the indexing model from the issue text.