CLN: assorted
- [ ] closes #xxxx (Replace xxxx with the GitHub issue number)
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

Thanks @jbrockmendel  This patch may have induced a potential regression. Please check the links below. If any ASVs are parameterized, the combinations of parameters that a regression has been detected appear as subbullets. This is a partially automated message.

 - https://asv-runner.github.io/asv-collection/pandas/#groupby.GroupByMethods.time_dtype_as_field
   - dtype='datetime'; method='bfill'; application='direct'; ncols=1
   - dtype='datetime'; method='bfill'; application='direct'; ncols=5
   - dtype='datetime'; method='bfill'; application='transformation'; ncols=1
   - dtype='datetime'; method='bfill'; application='transformation'; ncols=5
   - dtype='datetime'; method='diff'; application='direct'; ncols=1
   - dtype='datetime'; method='diff'; application='direct'; ncols=5
   - dtype='datetime'; method='diff'; application='transformation'; ncols=1
   - dtype='datetime'; method='diff'; application='transformation'; ncols=5
   - dtype='datetime'; method='ffill'; application='direct'; ncols=1
   - dtype='datetime'; method='ffill'; application='direct'; ncols=5
   - dtype='datetime'; method='ffill'; application='transformation'; ncols=1
   - dtype='datetime'; method='ffill'; application='transformation'; ncols=5
   - dtype='datetime'; method='first'; application='transformation'; ncols=1
   - dtype='datetime'; method='first'; application='transformation'; ncols=5
   - dtype='datetime'; method='last'; application='transformation'; ncols=1
   - dtype='datetime'; method='last'; application='transformation'; ncols=5
   - dtype='datetime'; method='max'; application='transformation'; ncols=1
   - dtype='datetime'; method='max'; application='transformation'; ncols=5
   - dtype='datetime'; method='min'; application='transformation'; ncols=1
   - dtype='datetime'; method='min'; application='transformation'; ncols=5
   - dtype='datetime'; method='quantile'; application='transformation'; ncols=1
   - dtype='datetime'; method='quantile'; application='transformation'; ncols=5
   - dtype='datetime'; method='shift'; application='direct'; ncols=1
   - dtype='datetime'; method='shift'; application='direct'; ncols=5
   - dtype='datetime'; method='shift'; application='transformation'; ncols=1
   - dtype='datetime'; method='shift'; application='transformation'; ncols=5
 - https://asv-runner.github.io/asv-collection/pandas/#inference.ToDatetimeCache.time_dup_seconds_and_unit
   - cache=T
 - https://asv-runner.github.io/asv-collection/pandas/#inference.ToDatetimeCache.time_dup_string_dates
   - cache=T
 - https://asv-runner.github.io/asv-collection/pandas/#inference.ToDatetimeCache.time_dup_string_dates_and_format
   - cache=T
 - https://asv-runner.github.io/asv-collection/pandas/#inference.ToDatetimeCache.time_dup_string_tzoffset_dates
   - cache=T
 - https://asv-runner.github.io/asv-collection/pandas/#io.csv.ParseDateComparison.time_read_csv_dayfirst
   - cache_dates=T
 - https://asv-runner.github.io/asv-collection/pandas/#io.csv.ParseDateComparison.time_to_datetime_dayfirst
   - cache_dates=T
 - https://asv-runner.github.io/asv-collection/pandas/#io.csv.ParseDateComparison.time_to_datetime_format_DD_MM_YYYY
   - cache_dates=T
 - https://asv-runner.github.io/asv-collection/pandas/#io.csv.ReadCSVParseSpecialDate.time_read_special_date
   - value='hm'; engine='c'
   - value='mdY'; engine='c'
 - https://asv-runner.github.io/asv-collection/pandas/#multiindex_object.SetOperations.time_operation
   - index_structure='monotonic'; dtype='datetime'; method='symmetric_difference'; sort=False
   - index_structure='non_monotonic'; dtype='datetime'; method='symmetric_difference'; sort=False
   - index_structure='non_monotonic'; dtype='datetime'; method='symmetric_difference'; sort=None
 - https://asv-runner.github.io/asv-collection/pandas/#reshape.ReshapeExtensionDtype.time_unstack_fast
   - dtype='
 - https://asv-runner.github.io/asv-collection/pandas/#reshape.ReshapeExtensionDtype.time_unstack_slow
   - dtype='
 - https://asv-runner.github.io/asv-collection/pandas/#reshape.SimpleReshape.time_stack
 - https://asv-runner.github.io/asv-collection/pandas/#reshape.SimpleReshape.time_unstack
 - https://asv-runner.github.io/asv-collection/pandas/#reshape.SparseIndex.time_unstack
