Add TIR Schedule and TIR support for consumer fusion

[guillon]

Motivation

TVM's legacy TE scheduling API is no longer available in recent TVM releases. Add an opt-in TIR scheduling path while preserving the existing TE path and XTC scheduling interface.

Description

This introduces schedulable/scheduled TVM expression abstractions that lower TE expressions to either TE schedules or TIR PrimFunc schedules. The TVM scheduler now emits TIR transformations for tiling, interchange, caching, buffering, unrolling, vectorization, parallelization, and producer/consumer fusion. Compilation, IR dumping, C emission, and library generation handle both schedule forms, including TVM version differences.

The TIR path can be selected with the backend tir_schedule option or the exploration CLI's --tir-schedule flag. LoopNest now records and displays fuse_producer_at and fuse_consumer_at annotations, with the latter exposed through the scheduler interface. FileCheck coverage includes scheduled matmul and fused producer/consumer graphs, while retaining TE fusion coverage.

Commits

• Fix schedule description dump expectations.
• Add TE-to-TIR lowering and TIR scheduling support.
• Add fuse_producer_at to LoopNest.
• Emit producer fusion for TVM TIR schedules.
• Add the fuse_consumer_at scheduling primitive and TVM TIR support.

Discussion

The TIR path is currently still optional, the TE scheduling remains the default. It my be changed in the future.

[codecov]

Codecov Report

❌ Patch coverage is 93.80531% with 14 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/xtc/backends/tvm/TVMOpsCompiler.py	93.40%	3 Missing and 3 partials ⚠️
src/xtc/backends/tvm/TVMCompiler.py	84.84%	4 Missing and 1 partial ⚠️
src/xtc/backends/tvm/TVMScheduler.py	96.29%	1 Missing and 2 partials ⚠️

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