Accept int64 VtValue for TYPE_INT with checked narrowing - Houdini 21

[rolledhand]

Compatibility:

build

Issues/Tickets:

• Related OpenMoonRay PR: Moonray macOS: update build compatibility for Houdini 21.0.680 openmoonray#228

Release notes comment:

Fixes Houdini 21 SceneVariables integer conversion by accepting 64-bit integer inputs for TYPE_INT attributes in ValueConverter.

Comments for the reviewer:

• This PR updates lib/hydramoonray/ValueConverter.cc.
• It fixes a Houdini 21 / Solaris integration issue where MoonRay received 64-bit integer values for __SceneVariables__ attributes that expect TYPE_INT.
• Before this change, MoonRay emitted repeated errors such as:
  • __SceneVariables__.* cannot convert long long to Int
• The fix adds:
  • 64-bit integer extraction for integral inputs
  • checked narrowing into MoonRay Int
  • enum index handling from 64-bit integer inputs
• Scope is intentionally narrow:
  • only TYPE_INT conversion behavior is updated
  • all other type paths remain unchanged

Look or scene setup change:

No intended look change. This is a Houdini/MoonRay value-conversion compatibility fix.

Special notes for production:

• This PR is intended to support Houdini 21.x Solaris/MoonRay workflows.
• It removes repeated long long -> Int conversion failures for SceneVariables in Houdini 21.
• No dependency or scene-format changes are intended.

Attention/Reviewers:

Checklist:

• Documentation has been updated.
• Includes new unit tests.
• Includes new RATS tests.