CLN: Delay converting bins to datetimelike until necessary

[mroeschke]

• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff

xref #20956, q/cut now returns datetimelike bins when retbins=True. Instead of always trying to convert bins to datetimelike (even when retbins=False), moving the conversion to _postprocess_for_cut until after retbins=True is checked

cc @jreback

[codecov]

Codecov Report

Merging #21724 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master   #21724   +/-   ##
=======================================
  Coverage   91.92%   91.92%           
=======================================
  Files         158      158           
  Lines       49702    49702           
=======================================
  Hits        45690    45690           
  Misses       4012     4012

Flag	Coverage Δ
#multiple	90.3% <100%> (ø)	⬆️
#single	42% <0%> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/core/reshape/tile.py	94.73% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 2b13605...c9ea5b5. Read the comment docs.

[jreback]

thanks!