PERF: ArrowExtensionArray.isna when zero nulls or all nulls
- [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/v2.1.0.rst` file if fixing a bug or adding a new feature.

Perf improvement in `ArrowExtensionArray.isna` when array has zero nulls or is all nulls. 

ASV added for `DataFrame.isna`:

```
       before           after         ratio
     [f9438649]       [3cb3cf47]
     <main>           <perf-arrow-isna>
-      32.1±0.5ms      7.95±0.08ms     0.25  frame_methods.Isna.time_isna('float64[pyarrow]')

SOME BENCHMARKS HAVE CHANGED SIGNIFICANTLY.
PERFORMANCE INCREASED.
```
thx @lukemanley 