Remove extra calls to all, .values(), and .keys() when constructing ignore_columns in DeepFeatureSynthesis

[sbadithe]

• In the init method for DeepFeatureSynthesis, we perform a type check on ignore_columns to make sure it maps strings to list of strings
• Currently, we iterate multiple times over the input to perform this type checking, then iterate again to create the ignore_columns data structure.
• By refactoring, we can reduce this to iterating once over the input. This reduces code complexity and computation required

[codecov]

Codecov Report

Merging #2397 (c5b757c) into main (9ce731e) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #2397   +/-   ##
=======================================
  Coverage   99.44%   99.44%           
=======================================
  Files         326      326           
  Lines       20205    20208    +3     
=======================================
+ Hits        20093    20096    +3     
  Misses        112      112           

Impacted Files	Coverage Δ
featuretools/synthesis/deep_feature_synthesis.py	99.77% <100.00%> (+<0.01%)	⬆️
...ols/tests/synthesis/test_deep_feature_synthesis.py	99.36% <100.00%> (ø)

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[rwedge]

LGTM