REF: prelim for fixing array_to_datetime

[jbrockmendel]

tslib.array_to_datetime has an unused format kwarg. This gets rid of it.

to_datetime (or more specifically, _convert_listlike_datetimes) has a bunch of boxing logic inside a try/except that doesn't need to be, obscures what Exception we're trying to catch. This moves that code outside the try/except and de-indents it. This overlaps with #23675.

xref #23722 (the conversation there less than the OP) cc @mroeschke

[pep8speaks]

Hello @jbrockmendel! Thanks for submitting the PR.

• There are no PEP8 issues in the file pandas/core/tools/datetimes.py !

[codecov]

Codecov Report

Merging #24000 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #24000      +/-   ##
==========================================
+ Coverage    92.3%    92.3%   +<.01%     
==========================================
  Files         161      161              
  Lines       51555    51557       +2     
==========================================
+ Hits        47589    47591       +2     
  Misses       3966     3966

Flag	Coverage Δ
#multiple	90.7% <100%> (ø)	⬆️
#single	42.44% <50%> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/core/tools/datetimes.py	85.53% <100%> (+0.08%)	⬆️

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[jreback]

thanks