Image reference specifying tag with digest should work

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Please run down the following list and make sure you've tried the usual "quick fixes":

- Search the issues already opened: https://github.com/googleapis/python-aiplatform/issues
- Search StackOverflow: https://stackoverflow.com/questions/tagged/google-cloud-platform+python

If you are still having issues, please be sure to include as much information as possible:

#### Environment details

- OS type and version: FROM python:3.10@sha256:0c896d9daf53a5fcd15ac064bf6731aafccb1cbceed40df4b3e30735666507eb
- Python version: `python --version` 3.10.6
- pip version: `pip --version`: 22.0.2
- `google-cloud-aiplatform` version: `pip show google-cloud-aiplatform` 1.18.3
- KFP version: 1.8.6

#### Steps to reproduce

Use image reference containing both tag and digest, e.g., gcr.io/some-project-id/some-product:0.0.1@sha256:0123456789abcedf0123456789abcedf0123456789abcedf0123456789abcedf

Using either tag (e.g., gcr.io/some-project-id/some-product:0.0.1) or digest (e.g., gcr.io/some-project-id/some-product@sha256:0123456789abcedf0123456789abcedf0123456789abcedf0123456789abcedf) works.

Expected image reference including both tag and digest is very useful for identifying correct images which is complex with just using digest.

See https://github.com/kubeflow/pipelines/issues/8490 for reference.

#### Expected result

Pipeline should run but receiving google.api_core.exceptions.InvalidArgument: 400 Invalid image URI gcr.io/some-project-id/some-product@sha256:0123456789abcedf0123456789abcedf0123456789abcedf0123456789abcedf instead.

#### Code example

```python
# example
```

#### Stack trace
```
Traceback (most recent call last):
File "/home/user/product/venv/lib/python3.10/site-packages/google/api_core/grpc_helpers.py", line 72, in error_remapped_callable
return callable_(*args, **kwargs)
File "/home/user/product/venv/lib/python3.10/site-packages/grpc/_channel.py", line 946, in __call__
return _end_unary_response_blocking(state, call, False, None)
File "/home/user/product/venv/lib/python3.10/site-packages/grpc/_channel.py", line 849, in _end_unary_response_blocking
raise _InactiveRpcError(state)
grpc._channel._InactiveRpcError: <_InactiveRpcError of RPC that terminated with:
status = StatusCode.INVALID_ARGUMENT
details = "Invalid image URI gcr.io/some-project-id/some-product@sha256:0123456789abcedf0123456789abcedf0123456789abcedf0123456789abcedf."
debug_error_string = "UNKNOWN:Error received from peer ipv4:172.217.13.106:443 {grpc_message:"Invalid image URI gcr.io/some-project-id/some-product@sha256:0123456789abcedf0123456789abcedf0123456789abcedf0123456789abcedf.", grpc_status:3, created_time:"2022-11-22T00:00:00.000000000+00:00"}"
>

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/home/user/product/venv/lib/python3.10/site-packages/google/api_core/grpc_helpers.py", line 74, in error_remapped_callable
raise exceptions.from_grpc_error(exc) from exc
google.api_core.exceptions.InvalidArgument: 400 Invalid image URI gcr.io/some-project-id/some-product@sha256:0123456789abcedf0123456789abcedf0123456789abcedf0123456789abcedf.
```

Making sure to follow these steps will guarantee the quickest resolution possible.

Thanks!