Expose FlexVol `autosize` and `fractionalReserve` as ontap-san (iSCSI) backend options

[shajia-deshaw]

Could we expose ONTAP FlexVol's:

• autosize configs (mode - off/grow/grow_shrink, grow threshold %, max size etc.)
• And also fractionalReserve.

as ontap-san (iSCSI) backend options. Per the docs, they don't seem exposed currently apart from the related spaceReserve / spaceAllocation / snapshotReserve.

ONTAP docs:

• ONTAP volume autosize
• ONTAP fractional-reserve