Add test to ensure positive_label passed properly in AMLSearch

[bchen1116]

fix #3068

The main thing we have to make sure is to pass the label encoder parameter to the stacked ensembler, since if the problem is classification, it will need these params. Most of this PR adds the logic to pass this param forward. We don't need to pass other parameters forward since we expect the pipelines to already be initialized with their respective parameters.

[codecov]

Codecov Report

Merging #3326 (cea8749) into main (1c74af9) will increase coverage by 0.1%.
The diff coverage is 100.0%.

@@           Coverage Diff           @@
##            main   #3326     +/-   ##
=======================================
+ Coverage   99.7%   99.7%   +0.1%     
=======================================
  Files        336     336             
  Lines      33282   33295     +13     
=======================================
+ Hits       33150   33163     +13     
  Misses       132     132             

Impacted Files	Coverage Δ
evalml/automl/automl_algorithm/automl_algorithm.py	100.0% <100.0%> (ø)
...valml/automl/automl_algorithm/default_algorithm.py	100.0% <100.0%> (ø)
...lml/automl/automl_algorithm/iterative_algorithm.py	97.4% <100.0%> (ø)
evalml/pipelines/utils.py	99.5% <100.0%> (ø)
.../automl_tests/test_automl_search_classification.py	96.6% <100.0%> (+0.1%)	⬆️

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[jeremyliweishih]

LGTM!

[jeremyliweishih]

LGTM, great work!

[chukarsten]

Just going to block this for a minute for clarity - this has the search_parameters changes in it, yes? Should it be a PR to your search_parameters PR? I don't think we should risk this getting merged before the other PR

[chukarsten]

should I be seeing a poop emoji here???

[bchen1116]

This was work done previously, I didn't change the resutls heh

[chukarsten]

@jeremyliweishih I rerequested your review now that the actual diff is readable

[jeremyliweishih]

LGTM, just a question about release cleanup and testing.

[chukarsten]

Awesome! Thank you, as always, Bryan.