[Enhancement] Use of the missing attribute on the DicomInstance class

Describe the bug
New version of pytype has found a new error, see below. Since this particular operator will still be used in the new versions of the App SDK, the flagged error needs to be investigated. Also note, there is currently no runtime error.

File "/home/mqin/src/monai-deploy-app-sdk/monai/deploy/operators/dicom_series_to_volume_operator.py", line 229, in prepare_series: No attribute 'first_pixel_on_slice_normal' on monai.deploy.core.domain.dicom_sop_instance.DICOMSOPInstance [attribute-error]

Steps/Code to reproduce bug

• Inspect the said file, and try to find the attribute, or
• In the pytype settings, make sure in the disable dose not contains 'attribute-error', and then run pytype on monai/deploy

Expected behavior
There should not be attribute-error and this particular error should not be disableed in the pytype settings.

Environment details (please complete the following information)

• OS/Platform: Linux
• Python Version: 3.7/3.8
• Method of MONAI Deploy App SDK install: [from source]
• SDK Version: 0.5/main

Additional context
This error is currently disabled in pytype report, so that the pull request build can succeed. Creating this bug is to schedule a real fix.