Enable AOTriton BWD V3 API

[Micky774]

Description

This is a follow-up to the earlier AOTriton update PR (#360). This one focuses on adopting the AOTriton V3 API for the BWD pass, including introducing a LazyTensor wrapper implementation (driven by an eager tensor as usual).

Follow-up for #360

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

Please list the changes introduced in this PR:

• Change A
• Change B

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

[Micky774]

Note this PR is not merge ready -- there are still some CI failures from the level 3 run that need to be corrected.