CLN: ArrowStringArray._cmp_method - use ChunkedArray.to_numpy()

[lukemanley]

• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.

Addresses minor TODO comment in ArrowStringArray._cmp_method.

Also, better perf:

import numpy as np
import pyarrow as pa

ca = pa.chunked_array([ 
    np.random.choice([0, 1], 1000),
    np.random.choice([0, 1], 1000),
], type=pa.bool_())

%timeit ca.to_pandas().values
45.9 µs ± 2.75 µs per loop (mean ± std. dev. of 7 runs, 10,000 loops each)

%timeit ca.to_numpy()
3.8 µs ± 273 ns per loop (mean ± std. dev. of 7 runs, 100,000 loops each)