feat: Update NetApp v1 API with Host Groups, Block Volumes, Cache Volumes, and Backup Restore

This CL introduces several new features and enhancements to the NetApp API:

-   **Host Groups:** Added a new `HostGroup` resource to manage collections of hosts for Block Volume access. Includes full CRUD operations.
-   **Block Volumes:** Enhanced the `Volume` resource to support `ISCSI` protocol and `BlockDevice` configurations.
-   **Cache Volumes:** Added `CacheParameters` to the `Volume` resource to support FlexCache volumes.
-   **Backup Restore:** Introduced a new `RestoreBackupFiles` RPC to restore individual files from a backup.
-   **CMEK for Backup Vaults:** Added fields to `BackupVault` to support Customer Managed Encryption Keys (CMEK).
-   **Storage Pool Type:** Added a `type` field to `StoragePool` to specify support for FILE, UNIFIED, or UNIFIED_LARGE_CAPACITY volumes.
-   **Location Metadata:** Added `has_ontap_proxy` flag.
-   Updated copyright year to 2026.

docs: A comment for field `backup_retention_policy` in message `.google.cloud.netapp.v1.BackupVault` is changed
docs: A comment for message `KmsConfig` is changed
docs: A comment for field `name` in message `.google.cloud.netapp.v1.KmsConfig` is changed
docs: A comment for field `crypto_key_name` in message `.google.cloud.netapp.v1.KmsConfig` is changed
docs: A comment for enum `SquashMode` is changed
docs: A comment for enum value `SQUASH_MODE_UNSPECIFIED` in enum `SquashMode` is changed
docs: A comment for field `anon_uid` in message `.google.cloud.netapp.v1.SimpleExportPolicyRule` is changed
PiperOrigin-RevId: 856056649

Source-Link: googleapis/googleapis@94aa4f5

Source-Link: googleapis/googleapis-gen@d3ff194
Copy-Tag: eyJwIjoiTmV0QXBwLy5Pd2xCb3QueWFtbCIsImgiOiJkM2ZmMTk0MjNjNmUxMzJmYmE5MTIwYTRmMjI2OTE5ZTJkNjNhNTAyIn0=

Author: gcf-owl-bot[bot]