WIP: Partial window of window support (second-order window)

[akeley98]

This is not a complete implementation. Full support would require changing scheduling operators to recognize windows as tensors (e.g. as a source for stage_mem) and/or also have to avoid creating invalid T.Window types or AttributeError-ing due to treating a T.Window as if it were a T.Tensor.

The key helper function is LoopIR.create_window_type which takes care of "inlining" the indexing effects of two windows together.

Fixes #594

[codecov]

Codecov Report

Attention: Patch coverage is 98.54015% with 2 lines in your changes missing coverage. Please review.

Project coverage is 88.34%. Comparing base (4bd40ca) to head (4302b63).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/exo/core/LoopIR.py	96.15%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #762      +/-   ##
==========================================
+ Coverage   88.23%   88.34%   +0.11%     
==========================================
  Files          93       93              
  Lines       21625    21716      +91     
==========================================
+ Hits        19080    19185     +105     
+ Misses       2545     2531      -14     

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