feat: [NetApp] Add ONTAP passthrough APIs (#9047)

* feat: Add ONTAP passthrough APIs

Adds the following new methods for direct ONTAP API interaction:
- ExecuteOntapPost
- ExecuteOntapGet
- ExecuteOntapDelete
- ExecuteOntapPatch

`StoragePoolType`
docs: A comment for field `source_volume` in message `.google.cloud.netapp.v1.Backup` is changed
docs: A comment for field `type` in message `.google.cloud.netapp.v1.StoragePool` is changed
docs: A comment for field `source_backup` in message `.google.cloud.netapp.v1.RestoreParameters` is changed

fix!: An existing value `UNIFIED_LARGE_CAPACITY` is removed from enum `StoragePoolType`

PiperOrigin-RevId: 889585893

Source-Link: googleapis/googleapis@a90dc55

Source-Link: googleapis/googleapis-gen@13a2f77
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