Add label encoder component to EvalML

[angela97lin]

Closes #2852

[codecov]

Codecov Report

Merging #2853 (47c3889) into main (d0a051f) will increase coverage by 0.1%.
The diff coverage is 97.1%.

@@           Coverage Diff           @@
##            main   #2853     +/-   ##
=======================================
+ Coverage   99.8%   99.8%   +0.1%     
=======================================
  Files        303     305      +2     
  Lines      28226   28353    +127     
=======================================
+ Hits       28145   28272    +127     
  Misses        81      81             

Impacted Files	Coverage Δ
evalml/pipelines/components/__init__.py	100.0% <ø> (ø)
evalml/tests/component_tests/test_utils.py	95.3% <33.4%> (ø)
...alml/pipelines/components/transformers/__init__.py	100.0% <100.0%> (ø)
...lines/components/transformers/encoders/__init__.py	100.0% <100.0%> (ø)
.../components/transformers/encoders/label_encoder.py	100.0% <100.0%> (ø)
evalml/tests/component_tests/test_components.py	99.3% <100.0%> (+0.1%)	⬆️
evalml/tests/component_tests/test_label_encoder.py	100.0% <100.0%> (ø)

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[freddyaboulton]

Looks good to me @angela97lin !

[freddyaboulton]

Makes sense to use init_series. This transformation would almost always change the schema.

[eccabay]

Nice, LGTM!

[eccabay]

Is there a reason we don't just use the parent Transformer's implementation for this?

[angela97lin]

I think nope, except we want a different docstring 😅 (which was incorrect, updating!)