Description

• Adds improved support for full-conversion and TRT engine export for a variety of models
• Automatically remove output repacking for convert_method_to_trt_engine calls, to improve parity between models which can be converted directly to TRT engines, and models which can be fully compiled
• Add new internal CompileSpec argument for lowering which indicates whether the lowering passes originate from a convert_method_to_trt_engine call or a regular compile call, which affects whether the lowering pass is applied
• Regular TorchScript graphs cannot have this pass applied, as it can otherwise break the output graph. Newer versions of Torch disallow graph outputs with 0 or 2+ arguments which are not packed in a struct
• Current lowering pass detects outputs which are flat Lists or Tuples of Tensors and returns the outputs as-is (direct from the TRT Engine), so the entire model can be converted to a single TRT engine

Fixes #1938
Fixes #1939

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist:

• [ x ] My code follows the style guidelines of this project (You can use the linters)
• [ x ] I have performed a self-review of my own code
• [ x ] I have commented my code, particularly in hard-to-understand areas and hacks
• [ x ] I have made corresponding changes to the documentation
• [ x ] I have added tests to verify my fix or my feature
• [ x ] New and existing unit tests pass locally with my changes
• [ x ] I have added the relevant labels to my PR in so that relevant reviewers are notified