Run iPhone benchmark on private devices (#10380)

Same as https://github.com/pytorch/executorch/pull/10192, but this is
for the private iPhone 15 devices. I will need to follow on this with
another PR to get the device pool name / id and maybe the device id

### Testing


https://hud.pytorch.org/benchmark/llms?startTime=Wed%2C%2016%20Apr%202025%2004%3A22%3A32%20GMT&stopTime=Wed%2C%2023%20Apr%202025%2004%3A22%3A32%20GMT&granularity=day&lBranch=apple-private-devices&lCommit=be72291c9b643581fedafaf8711d07fd5542b62d&rBranch=apple-private-devices&rCommit=be72291c9b643581fedafaf8711d07fd5542b62d&repoName=pytorch%2Fexecutorch&benchmarkName=&modelName=All%20Models&backendName=All%20Backends&modeName=All%20Modes&dtypeName=All%20DType&deviceName=All%20Devices&archName=All%20Platforms