PERF: maybe_promote
Test runtime for pandas/tests/indexing/multiindex/test_indexing_slow.py decreases from 30s to 14.5s.

See discussion around https://github.com/pandas-dev/pandas/pull/39692#issuecomment-1441051740
our asv site appears to be done, but locally a lot of the regressions im seeing since 1.5.0 are for `groupby.GroupByMethods.time_dtype_as_field('datetime', ...)` and profiling points at maybe_promote so im guessing this will address a bunch of those

cc @phofl  thx @jbrockmendel