Replace Vec with VecDeque for proper BFT queue behavior in NodeIter

[WilsonKuo]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 35.64%. Comparing base (6ab89bf) to head (82df1e8).

Files with missing lines	Patch %	Lines
algorithms/linfa-trees/src/decision_trees/iter.rs	0.00%	3 Missing ⚠️
...rithms/linfa-trees/src/decision_trees/algorithm.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #383      +/-   ##
==========================================
+ Coverage   35.60%   35.64%   +0.03%     
==========================================
  Files          97       97              
  Lines        6386     6386              
==========================================
+ Hits         2274     2276       +2     
+ Misses       4112     4110       -2     

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