Refactor/elemwise/kernel selection + dynamic fused inplace operations and broadcasting

[nathanielsimard]

Refactor elemwise fused kernels to use the new compilation settings to identify kernels instead of pre-compiling every possible combination and having a complex selection process. This allows support for dynamic partial in-place operations as well as avoiding the execution of broadcasting procedures in fused kernels when not necessary (a new kernel is going to be created). These are very finely grained optimizations; no real speed improvements are going to be noticeable at first, but with more aggressive fusion and a longer stream of operations fused, it will help in reducing allocated memory.

[louisfd]

LGTM

[codecov]

Codecov Report

Attention: Patch coverage is 91.45299% with 30 lines in your changes are missing coverage. Please review.

Project coverage is 85.34%. Comparing base (bdec8d5) to head (a60e068).

Files	Patch %	Lines
crates/burn-wgpu/src/codegen/compilation.rs	87.06%	26 Missing ⚠️
crates/burn-wgpu/src/codegen/dialect/gpu/scope.rs	80.00%	2 Missing ⚠️
crates/burn-wgpu/src/fusion/elemwise/kernel.rs	98.59%	1 Missing ⚠️
crates/burn-wgpu/src/fusion/kernel.rs	95.23%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1359      +/-   ##
==========================================
- Coverage   85.40%   85.34%   -0.06%     
==========================================
  Files         591      591              
  Lines       67468    67497      +29     
==========================================
- Hits        57618    57604      -14     
- Misses       9850     9893      +43     

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