Add Mooncake extension for propagate copy_xj (+) fast path and enable tests

[Parvm1102]

GNN AD Benchmark Results

The rules matched for the following layers, the improvements and the benchmarks are listed below, all layers pass the gradient correctness benchmarks:

GCNConv

[n=512]
  forward: ok   grad-check PASS

  Zygote             Zyg     0.541 ms /   1136 alloc
  Mooncake + RULE     MC     2.443 ms /    401 alloc   (MC+rule / Zyg =  4.52x)
  Mooncake - rule     MC     9.628 ms /    582 alloc   (no-rule / Zyg = 17.80x)

  >>> RULE SPEEDUP (no-rule / +rule) =  3.94x

[n=2048]
  forward: ok   grad-check PASS

  Zygote             Zyg     1.752 ms /   1136 alloc
  Mooncake + RULE     MC    10.260 ms /    401 alloc   (MC+rule / Zyg =  5.86x)
  Mooncake - rule     MC    37.645 ms /    582 alloc   (no-rule / Zyg = 21.49x)

  >>> RULE SPEEDUP (no-rule / +rule) =  3.67x

GraphConv

[n=512]
  forward: ok   grad-check PASS

  Zygote             Zyg     0.486 ms /    470 alloc
  Mooncake + RULE     MC     1.482 ms /    198 alloc   (MC+rule / Zyg =  3.05x)
  Mooncake - rule     MC     7.895 ms /    377 alloc   (no-rule / Zyg = 16.26x)

  >>> RULE SPEEDUP (no-rule / +rule) =  5.33x

[n=2048]
  forward: ok   grad-check PASS

  Zygote             Zyg     1.806 ms /    470 alloc
  Mooncake + RULE     MC     6.200 ms /    198 alloc   (MC+rule / Zyg =  3.43x)
  Mooncake - rule     MC    30.904 ms /    377 alloc   (no-rule / Zyg = 17.11x)

  >>> RULE SPEEDUP (no-rule / +rule) =  4.98x

SAGEConv (aggr=+)

[n=512]
  forward: ok   grad-check PASS

  Zygote             Zyg     0.579 ms /    462 alloc
  Mooncake + RULE     MC     1.868 ms /    190 alloc   (MC+rule / Zyg =  3.23x)
  Mooncake - rule     MC     8.168 ms /    367 alloc   (no-rule / Zyg = 14.11x)

  >>> RULE SPEEDUP (no-rule / +rule) =  4.37x

[n=2048]
  forward: ok   grad-check PASS

  Zygote             Zyg     1.426 ms /    462 alloc
  Mooncake + RULE     MC     7.171 ms /    190 alloc   (MC+rule / Zyg =  5.03x)
  Mooncake - rule     MC    32.122 ms /    367 alloc   (no-rule / Zyg = 22.52x)

  >>> RULE SPEEDUP (no-rule / +rule) =  4.48x

GINConv

[n=512]
  forward: ok   grad-check PASS

  Zygote             Zyg     0.425 ms /    497 alloc
  Mooncake + RULE     MC     1.023 ms /    200 alloc   (MC+rule / Zyg =  2.41x)
  Mooncake - rule     MC     7.461 ms /    379 alloc   (no-rule / Zyg = 17.56x)

  >>> RULE SPEEDUP (no-rule / +rule) =  7.29x

[n=2048]
  forward: ok   grad-check PASS

  Zygote             Zyg     1.174 ms /    497 alloc
  Mooncake + RULE     MC     3.858 ms /    200 alloc   (MC+rule / Zyg =  3.29x)
  Mooncake - rule     MC    29.031 ms /    379 alloc   (no-rule / Zyg = 24.72x)

  >>> RULE SPEEDUP (no-rule / +rule) =  7.53x

SGConv (k=2)

[n=512]
  forward: ok   grad-check PASS

  Zygote             Zyg     2.704 ms /   1813 alloc
  Mooncake + RULE     MC     4.545 ms /    491 alloc   (MC+rule / Zyg =  1.68x)
  Mooncake - rule     MC    17.955 ms /    854 alloc   (no-rule / Zyg =  6.64x)

  >>> RULE SPEEDUP (no-rule / +rule) =  3.95x

[n=2048]
  forward: ok   grad-check PASS

  Zygote             Zyg     5.115 ms /   1813 alloc
  Mooncake + RULE     MC    15.896 ms /    491 alloc   (MC+rule / Zyg =  3.11x)
  Mooncake - rule     MC    71.492 ms /    854 alloc   (no-rule / Zyg = 13.98x)

  >>> RULE SPEEDUP (no-rule / +rule) =  4.50x

TAGConv (k=2)

[n=512]
  forward: ok   grad-check PASS

  Zygote             Zyg     2.625 ms /   1858 alloc
  Mooncake + RULE     MC     6.983 ms /    524 alloc   (MC+rule / Zyg =  2.66x)
  Mooncake - rule     MC    18.938 ms /    887 alloc   (no-rule / Zyg =  7.22x)

  >>> RULE SPEEDUP (no-rule / +rule) =  2.71x

[n=2048]
  forward: ok   grad-check PASS

  Zygote             Zyg     8.645 ms /   1858 alloc
  Mooncake + RULE     MC    21.477 ms /    524 alloc   (MC+rule / Zyg =  2.48x)
  Mooncake - rule     MC    85.246 ms /    887 alloc   (no-rule / Zyg =  9.86x)

  >>> RULE SPEEDUP (no-rule / +rule) =  3.97x

GatedGraphConv (L=2)

[n=512]
  forward: ok   grad-check PASS

  Zygote             Zyg     7.233 ms /   3182 alloc
  Mooncake + RULE     MC    15.051 ms /   2298 alloc   (MC+rule / Zyg =  2.08x)
  Mooncake - rule     MC    31.563 ms /   2661 alloc   (no-rule / Zyg =  4.36x)

  >>> RULE SPEEDUP (no-rule / +rule) =  2.10x

[n=2048]
  forward: ok   grad-check PASS

  Zygote             Zyg    13.064 ms /   3182 alloc
  Mooncake + RULE     MC    58.372 ms /   2298 alloc   (MC+rule / Zyg =  4.47x)
  Mooncake - rule     MC   108.064 ms /   2661 alloc   (no-rule / Zyg =  8.27x)

  >>> RULE SPEEDUP (no-rule / +rule) =  1.85x

The PR also enables Mooncake testing in the same way currently as done here:

https://github.com/JuliaGraphs/GraphNeuralNetworks.jl/blob/f09fcc4af170c1d87dc1d51648c3a015357fea93/GraphNeuralNetworks/test/test_module.jl

I will fix the format as mentioned in #676 in a future PR.

[Parvm1102]

@CarloLucibello Could you please review this?