[iluvatar]add vendor/iluvatar backend

[DannyP0]

Description

[iluvatar]add vendor/iluvatar backend

Fixes # (issue)

Type of change

• Documentation change (change only to the documentation, either a fix or a new content)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Infra/Build change
• Code refactoring

Changes

add vendor/iluvatar backend

Checklist:

• I have read and followed the contributing guidelines
• The functionality is complete
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[CLAassistant]

All committers have signed the CLA.

[lxd-cumt]

The native FlashAttention in Iluvatar has not been integrated—is there any issue with it?

[DannyP0]

No issues at all. FlagOS is fully supported and works well here. Iluvatar's native FlashAttention is still in integration and will be added in a follow-up.

[lxd-cumt]

LGTM