(pipelines): (unable to share role between the automatic assets generation codebuild projects)

### Describe the bug

If you have a stage that generates a lot of assets, the codepipeline role policy will get tons of stuff like this:

```
{
"Action": "sts:AssumeRole",
"Resource": "arn:aws:iam::XXXXX:role/asset1dockerassets10",
"Effect": "Allow"
}
```

eventually it falls appart and fails with: "Maximum policy size of 10240 bytes exceeded for ..."

It should be possible to pass a role when configuring the codepipeline, used for asset-generation (or pr account) or just a flag: "optOutOfLeastPrivilegeForAssetGeneration"

### Expected Behavior

The generated CF-stack not to increase with every new generated asset.

### Current Behavior

The generated CF-stack increases with every asset added to a pipeline stage.

### Reproduction Steps

create a codepipelinestack and observe that a role is generated for each stage asset.

### Possible Solution

_No response_

### Additional Information/Context

_No response_

### CDK CLI Version

2.49.0

### Framework Version

_No response_

### Node.js Version

not relevant

### OS

not relevant

### Language

Typescript

### Language Version

_No response_

### Other information

_No response_

Start by reproducing the issue with a codepipelinestack containing many assets and inspect the generated CF-stack and CodePipeline role policy. Determine whether the intended fix is a shared asset-generation role or an opt-out flag, then verify that adding assets no longer causes the policy to exceed the 10240-byte limit.

Written by the indexing model from the issue text.