(transform): convert to csl_stencil.apply

[n-io]

This PR implements the conversion to csl_stencil.apply op as outlined in Step 2 of #2747

The csl_stencil.apply op combines a csl_stencil.prefetch (symmetric buffer communication across a given stencil shape) with a stencil.apply.

The transformation consists of several steps:

• When rewriting a stencil.apply, select the csl_stencil.prefetch with the biggest memory overhead (if several are present) to be fused with the apply op into a csl_stencil.apply
• Find a suitable split of ops to be divided across the two code blocks
  • Re-order arithmetic e.g. (a+b)+c -> (c+a)+b to access, consume, and reduce data of neighbours (for input stencil only)
  • Move this into first code block, move all other ops into second code block
  • Fallback strategy: Move everything into first code block
• Add tensor.InsertSliceOp to insert computed chunk into returned z-value tensor
• Set up code block args
• Move ops into new regions according to determined split
• Translate arg usage to match new block args
• Set up yield ops
• Run tensor update shape on chunk region

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.84%. Comparing base (1825c02) to head (f531936).
Report is 19 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2803      +/-   ##
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+ Coverage   89.79%   89.84%   +0.04%     
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  Files         394      397       +3     
  Lines       48747    49342     +595     
  Branches     7471     7592     +121     
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+ Hits        43774    44332     +558     
- Misses       3793     3815      +22     
- Partials     1180     1195      +15     

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