PERF: ArrowExtensionArray.searchsorted
- [x] [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
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [x] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [x] Added an entry in the latest `doc/source/whatsnew/v2.0.0.rst` file if fixing a bug or adding a new feature.

Perf improvement in `ArrowExtensionArray.searchsorted`: 

```
import pandas as pd
import numpy as np

arr = pd.array(np.arange(10**6), dtype="int64[pyarrow]")

%timeit arr.searchsorted(500)

# 367 ms ± 2.52 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)         <- main
# 21.3 µs ± 1.18 µs per loop (mean ± std. dev. of 7 runs, 10,000 loops each)  <- PR
```
Thanks @lukemanley 