fix(storage): add missing VirtioScsi resource_reference types

[RedZapdos123]

Description:

Issue #489 reported that two Virtio SCSI resource reference fields were missing explicit google.api.resource_reference typing.

VirtioScsiLun.target_name_ref and StatsVirtioScsiLunRequest.controller_name_ref referenced other storage resources, but unlike nearby fields in the same proto they only declared field behavior. That left the schema inconsistent and omitted the concrete target resource metadata expected for resource-reference fields.

This PR adds the missing resource reference annotations:

• target_name_ref -> opi_api.storage.v1/VirtioScsiTarget
• controller_name_ref -> opi_api.storage.v1/VirtioScsiController

It also refreshes the checked-in generated Go and Python descriptor bindings for frontend_virtio_scsi.proto, so the committed SDK artifacts now carry the same metadata as the source schema.

Closes #489.

Checklist:

• I added the missing resource reference annotations in the source proto.
• I refreshed the checked-in generated Go and Python descriptor bindings for frontend_virtio_scsi.proto.
• I ran focused Buf linting in WSL using buf lint --path storage/frontend_virtio_scsi.proto.
• I ran focused api-linter checks against Buf-built descriptor sets for both main and this PR version of storage/frontend_virtio_scsi.proto.
• The focused api-linter result is unchanged by this PR: both before and after report only the same pre-existing core::0191::proto-package finding.

Why the generated diff is large:

The functional change is small, but the checked-in generated files embed serialized protobuf descriptors. Adding two resource_reference options changes those descriptor blobs and their offsets, which shows up as a large textual diff in generated Go/Python output.

Before the fix:

string target_name_ref = 2 [(google.api.field_behavior) = REQUIRED];
string controller_name_ref = 2 [(google.api.field_behavior) = OPTIONAL];

These fields had no explicit target resource typing.

After the fix:

string target_name_ref = 2 [
  (google.api.field_behavior) = REQUIRED,
  (google.api.resource_reference).type = "opi_api.storage.v1/VirtioScsiTarget"
];

string controller_name_ref = 2 [
  (google.api.field_behavior) = OPTIONAL,
  (google.api.resource_reference).type = "opi_api.storage.v1/VirtioScsiController"
];

The source schema and checked-in generated descriptors now carry the correct resource reference metadata.