Provide useful debugging info when all pipelines are NaN

[eccabay]

Adds a new errors attribute to the AutoMLSearch object which provides information on all the errors that occurred while running search. The error thrown if all pipelines in a batch are None or NaN references this so devs have more useful information during debugging.

[codecov]

Codecov Report

Merging #3702 (6c0125e) into main (07d7af6) will increase coverage by 0.1%.
The diff coverage is 100.0%.

@@           Coverage Diff           @@
##            main   #3702     +/-   ##
=======================================
+ Coverage   99.7%   99.7%   +0.1%     
=======================================
  Files        339     339             
  Lines      34451   34465     +14     
=======================================
+ Hits       34324   34338     +14     
  Misses       127     127             

Impacted Files	Coverage Δ
evalml/automl/utils.py	96.9% <ø> (ø)
evalml/tests/automl_tests/dask_test_utils.py	100.0% <ø> (ø)
...ests/automl_tests/parallel_tests/test_cf_engine.py	100.0% <ø> (ø)
...ts/automl_tests/parallel_tests/test_dask_engine.py	100.0% <ø> (ø)
evalml/tests/automl_tests/test_engine_base.py	100.0% <ø> (ø)
evalml/automl/automl_search.py	99.5% <100.0%> (+0.1%)	⬆️
evalml/automl/callbacks.py	100.0% <100.0%> (ø)
evalml/tests/automl_tests/test_automl.py	99.5% <100.0%> (+0.1%)	⬆️

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[chukarsten]

LGTM! Thanks so much for this. I think we might need a follow up story maybe to pretty print the dictionary or something, but this is a big step in the right direction.