Add NodeFormer model and example

[xnuohz]

Issue

• From Graph Transformer Enhancement #9751
• Adds an example for training NodeFormer model on ogbn-arxiv dataset.

Usage

python examples/ogbn_train.py --model nodeformer

Highlight

Result

• GAT and SAGE use batch_size=1024
• SGFormer and Polynormer use batch_size=512, otherwise OOM

Dataset	GAT	SAGE	SGFormer	Polynormer	NodeFormer
ogbn-arxiv	68.53%	70.17%	71.86%	65.90%	66.98%

[codecov]

Codecov Report

❌ Patch coverage is 81.11888% with 54 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.06%. Comparing base (c211214) to head (7ad95d4).
⚠️ Report is 142 commits behind head on master.

Files with missing lines	Patch %	Lines
torch_geometric/nn/models/nodeformer.py	81.05%	54 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #10409      +/-   ##
==========================================
- Coverage   86.11%   85.06%   -1.05%     
==========================================
  Files         496      511      +15     
  Lines       33655    36250    +2595     
==========================================
+ Hits        28981    30836    +1855     
- Misses       4674     5414     +740     

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[puririshi98]

@xnuohz plz get CI passing

[puririshi98]

LGTM just get CI green

[puririshi98]

@rusty1s @akihironitta @wsad1 ready for final review/merge

[puririshi98]

@xnuohz can you explain where we are ensuring attention is not being done across the full minibatch? we should be utilizing the batch tensor, no? (remember what we had to change for sgformer)