Respect StorageClass provisioner capabilities for PVC access modes

[skanakal]

Summary

PR Checklist

• Is this a multi-tenancy feature/bug?
  • Yes, the relevant RBAC changes are at:
• Do we need to backport changes to the old Rancher UI, such as RKE1?
  • Yes, the relevant PR is at:
• Are backend engineers aware of UI changes?
  • Yes, the backend owner is:

Related Issue #

harvester/harvester#9662

Occurred changes and/or fixed issues

Technical notes summary

• The getAccessMode() method in HarvesterVolume.vue only checked for:

  • LVM driver
  • Longhorn V2
    All other provisioners defaulted to ReadWriteMany, regardless of their actual capabilities.
    Solution:

This change only adjusts access mode selection for filesystem volumes created using block-backed CSI drivers, avoiding RWX where unsupported

Areas or cases that should be tested

1. Create volume with NetApp Trident ONTAP SAN → PVC gets accessModes: ['ReadWriteOnce'] → Provisions successfully
2. Create volume with Longhorn → Still gets correct mode (RWO for V2, RWX for V1)
3. Create volume with LVM → Still gets ReadWriteOnce
4. Create volume with unknown provisioner → Defaults to ReadWriteMany (backward compatible)

Areas which could experience regressions

Screenshot/Video

[skanakal]

@torchiaf Can you please review this pr?