Add `reverse` support in `aggregation_resolver`

[lightaime]

This PR added the reverse support in aggregation_resolver to resolve Aggregation to strings. This will keep message_and_aggregate functionality intact if an aggr is FUSE_AGGRS but passed with Aggregation instance.

Addresses https://github.com/pyg-team/pytorch_geometric/issues/4712.

[codecov[bot]]

Codecov Report

Merging #5084 (1b132c1) into master (412ae53) will decrease coverage by 1.88%. The diff coverage is 83.87%.

@@            Coverage Diff             @@
##           master    #5084      +/-   ##
==========================================
- Coverage   84.86%   82.97%   -1.89%     
==========================================
  Files         332      332              
  Lines       18304    18324      +20     
==========================================
- Hits        15534    15205     -329     
- Misses       2770     3119     +349     

Impacted Files	Coverage Δ
torch_geometric/nn/conv/message_passing.py	98.84% <75.00%> (+<0.01%)	:arrow_up:
torch_geometric/nn/resolver.py	87.67% <85.18%> (-6.33%)	:arrow_down:
torch_geometric/nn/models/dimenet_utils.py	0.00% <0.00%> (-75.52%)	:arrow_down:
torch_geometric/nn/models/dimenet.py	14.51% <0.00%> (-53.00%)	:arrow_down:
torch_geometric/nn/conv/utils/typing.py	81.25% <0.00%> (-17.50%)	:arrow_down:
torch_geometric/profile/profile.py	32.94% <0.00%> (-15.30%)	:arrow_down:
torch_geometric/nn/inits.py	67.85% <0.00%> (-7.15%)	:arrow_down:
torch_geometric/transforms/add_self_loops.py	94.44% <0.00%> (-5.56%)	:arrow_down:
torch_geometric/io/tu.py	93.90% <0.00%> (-2.44%)	:arrow_down:
... and 10 more

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[Padarn]

This seems important, but I wonder if we could just define the equivalent aggregation on the aggregation class itself.

class SomeAggregation:
    @property
    def resolve_str():
        return "some_aggregation"

Not sure if its better. Just a thoguht.

[lightaime]

This seems important, but I wonder if we could just define the equivalent aggregation on the aggregation class itself.

class SomeAggregation:
    @property
    def resolve_str():
        return "some_aggregation"

Not sure if its better. Just a thoguht.

Thanks for the suggestion. I am open to this solution as well.

[rusty1s]

Sorry for the delay in review.