e2e: test build records export

[crazy-max]

relates to docker/build-push-action#1388

[crazy-max]

Ok it seems we have an issue when exporting build records with kubernetes driver: https://github.com/docker/buildx/actions/runs/16618088830/job/47015660807?pr=3344#step:9:321

+ docker buildx --builder=buildx-test-81a84e3206624d8ccfa87d0671c83caf history ls
}BUILD ID                    NAME                       STATUS      CREATED AT               DURATION   
b3lghrsw4kokqcu6o9noohf5r   buildx-output.gOYQhHjKHB   Completed   Less than a second ago   0.2s       
y3i6edhnuqzvg49hhh258rh4h   buildx-output.gOYQhHjKHB   Completed   1 second ago             0.9s       
y3i6edhnuqzvg49hhh258rh4h   buildx-output.gOYQhHjKHB   Completed   1 second ago             0.8s       
+ docker buildx --builder=buildx-test-81a84e3206624d8ccfa87d0671c83caf history export --finalize --all --output /tmp/buildx-output.gOYQhHjKHB/records.dockerbuild
ERROR: failed to export: failed to export record: failed to load trace descriptor: failed to get info: NotFound: rpc error: code = NotFound desc = content digest sha256:ff40cfe817248c69ba040c07b373d9cb444b89d5b65f8f4125ba796652c2e93f: not found

Seems to be an issue with trace descriptor even when finalizing.