PERF: DatetimeIndex comparison with Timestamp mismatched resos

[jbrockmendel]

• closes PERF: performance problem when comparing timestamp to datetimindex  #52080 (Replace xxxx with the GitHub issue number)
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations 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.

import pandas as pd

rg = pd.date_range("2020-01-01", periods=100_000, freq="s")

ts_ns = pd.Timestamp("1996-01-01 00:00:00.00000000000")
ts_s = pd.Timestamp("1996-01-01")

%timeit rg < ts_s
3.68 ms ± 138 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)   # <- main
139 µs ± 3.96 µs per loop (mean ± std. dev. of 7 runs, 10,000 loops each)  # <- PR

@MarcoGorelli can you confirm this closes #52080

[MarcoGorelli]

Looks good to me, can confirm this resolves the issue - both paths are covered, so should be fine

@phofl any objections?

[MarcoGorelli]

let's ship it

[MarcoGorelli]

thanks @jbrockmendel

[phofl]

Thx for taking care of this.