Fix Milvus installation in OpenShift

[shengnuo]

Milvus is crashing when it's installed in a custom namespace OpenShift with the following error message
2025/02/27 07:46:13 write failed: open /milvus/configs/milvus.yaml: permission denied

This stems from the restricted-v2 SCC in OpenShift.
By default, OpenShift uses the most restricted SCC restricted-v2 for service accounts in nemo namespace. When such SCC is applied, the following securityContext is added to the Milvus container.

securityContext:
allowPrivilegeEscalation: false
capabilities:
drop:
- ALL
runAsNonRoot: true
runAsUser: 1000790000

This makes the main container unable to read the /milvus/configs/milvus.yaml file created by the init container.

This MR fixes the issue by creating a dedicated service account for Milvus, and assigning the SCC anyuid to the service account.

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[shivamerla]

LGTM