dialects: (dmp) Move to subfolder, add scatter/gather and lowering

[AntonLydike]

This moves all the dmp stuff into a subfolder and adds a lowering for scatter/gather

[codecov]

Codecov Report

Patch coverage: 51.89% and project coverage change: -0.18 ⚠️

Comparison is base (546d604) 87.09% compared to head (696e6f9) 86.92%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1053      +/-   ##
==========================================
- Coverage   87.09%   86.92%   -0.18%     
==========================================
  Files         127      129       +2     
  Lines       19612    19703      +91     
  Branches     2971     2981      +10     
==========================================
+ Hits        17082    17126      +44     
- Misses       2023     2070      +47     
  Partials      507      507              

Impacted Files	Coverage Δ
xdsl/transforms/experimental/dmp/scatter_gather.py	33.33% <33.33%> (ø)
xdsl/transforms/experimental/dmp/decompositions.py	56.86% <56.86%> (ø)
...sforms/experimental/dmp/stencil_global_to_local.py	24.50% <57.14%> (ø)
xdsl/dialects/experimental/dmp.py	49.27% <89.47%> (+2.33%)	⬆️
xdsl/xdsl_opt_main.py	98.18% <100.00%> (+0.03%)	⬆️

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