ovf: Support non-file backed disks, deployment configs, and vApp property qualifiers

[akutz]

Description

This PR extends the ovf package’s OVF→ConfigSpec behavior in three areas: file-backed vs empty disks, OVF property types/qualifiers per DSP0243, and explicit deployment configuration selection.

1. File-backed disks in OVF→ConfigSpec

• Behavior: Treat OVF disks that have ovf:fileRef as file-backed and all others as capacity-only (empty) in the generated ConfigSpec.
• Implementation:
  • Build a fileRefs map from Envelope.References and pass it through toHardware into toVirtualDisk.
  • For disks with a DiskSection fileRef, set backing FileName from path.Base(File.Href); empty disks keep an empty backing name.
  • Set FileOperation to Create for empty disks and to empty string for file-backed disks (existing file).
• Tests/fixtures: fixtures/mixed-disks.ovf (one file-backed, one empty), plus tests for backing FileName, FileOperation, and file-backed disk name from path.Base(File.Href).

2. Parse OVF property qualifiers per DSP0243

• OVF→vApp type mapping (DSP0243 Table 6): Map uint8/sint8/…/sint64 → int, String → string, Boolean → boolean, real32/real64 → real. Honor ovf:password so string becomes password.
• Qualifiers (DSP0243 9.5.1 Table 7): Parse ovf:qualifiers: MinLen, MaxLen, ValueMap for string; ValueMap for integer types.
• VAppPropertyInfo.Type: Build from base type and qualifiers (e.g. MinLen(1),MaxLen(65535) → string(1..65535), ValueMap → string["a","b"] or int(min..max)).
• Usage: Use the computed type in toVAppConfig for property Info.Type and in parseVAppConfigValue so qualifier-derived constraints are applied.
• Tests: Qualifier-derived types and root_pwd Type "password" when ovf:password="true".

3. Explicit deployment configuration

• API: Add DeploymentConfiguration to ToConfigSpecOptions to select which deployment option (DeploymentOptionSection) to use; if empty, use the default or the first configuration.
• Resolution: New resolveDeploymentConfiguration() resolves by name and validates against the envelope’s DeploymentOptionSection.
• Behavior: Only elements (e.g. VirtualHardware Item, ProductSection Property) that match the selected configuration or have no configuration are included.
• Tests/fixtures: Deployment config selection (including invalid name), OVF property types → vAppPropertyInfo.Type, and file-ref path in disk backing. Fixtures: deployment-configs.ovf, property-types.ovf, file-ref-path.ovf.

Closes: #(issue-number) NA

How Has This Been Tested?

go test -v ./ovf

Guidelines

Please read and follow the CONTRIBUTION guidelines of this project.

[lubronzhan]

LGTM