Added BytesIO support to PipelineBase.load()

[cp2boston]

Pull Request Description

Added support for BytesIO input to PipelineBase.load(), primarily to support VFS

Fixes #4178

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #4179 (2469770) into main (ee540f1) will increase coverage by 0.1%.
The diff coverage is 100.0%.

@@           Coverage Diff           @@
##            main   #4179     +/-   ##
=======================================
+ Coverage   99.7%   99.7%   +0.1%     
=======================================
  Files        349     349             
  Lines      37797   37809     +12     
=======================================
+ Hits       37680   37692     +12     
  Misses       117     117             

Impacted Files	Coverage Δ
evalml/pipelines/pipeline_base.py	98.5% <100.0%> (+0.1%)	⬆️
evalml/tests/pipeline_tests/test_pipelines.py	99.9% <100.0%> (+0.1%)	⬆️

[jeremyliweishih]

Nit but otherwise LGTM!