PERF: DatetimeIndex comparison with Timestamp mismatched resos
- [x] closes #52080 (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.

```
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
let's ship it thanks @jbrockmendel 