perf: Use bulk-NULL builder in replace

[neilconway]

Which issue does this PR close?

• Closes Optimize replace to use bulk-NULL string builder #21848.

Rationale for this change

We can use the new bulk-NULL string builder APIs to reduce NULL handling overhead in replace. There is a further opportunity for optimization once arrow/arrow-rs#9692 lands.

Benchmarks:

• replace size=1024/replace_string_ascii_single [str_len=32]: 17.42 µs → 14.35 µs, −17.71%
• replace size=1024/replace_string_view [str_len=32]: 21.23 µs → 18.89 µs, −11.05%
• replace size=1024/replace_string [str_len=32]: 20.42 µs → 18.51 µs, −9.36%
• replace size=1024/replace_large_string [str_len=32]: 20.83 µs → 18.42 µs, −11.60%
• replace size=1024/replace_string_ascii_single [str_len=128]: 10.61 µs → 10.37 µs, −2.22%
• replace size=1024/replace_string_view [str_len=128]: 28.37 µs → 28.03 µs, −1.21%
• replace size=1024/replace_string [str_len=128]: 27.96 µs → 28.03 µs, +0.25% (noise)
• replace size=1024/replace_large_string [str_len=128]: 28.15 µs → 27.95 µs, −0.70% (noise)
• replace size=4096/replace_string_ascii_single [str_len=32]: 68.40 µs → 56.15 µs, −17.94%
• replace size=4096/replace_string_view [str_len=32]: 85.95 µs → 76.84 µs, −10.61%
• replace size=4096/replace_string [str_len=32]: 82.79 µs → 74.71 µs, −9.76%
• replace size=4096/replace_large_string [str_len=32]: 85.32 µs → 75.14 µs, −11.94%
• replace size=4096/replace_string_ascii_single [str_len=128]: 38.35 µs → 39.10 µs, +1.96% (small regression)
• replace size=4096/replace_string_view [str_len=128]: 132.77 µs → 128.08 µs, −3.53%
• replace size=4096/replace_string [str_len=128]: 127.71 µs → 128.29 µs, +0.46% (noise)
• replace size=4096/replace_large_string [str_len=128]: 131.97 µs → 128.68 µs, −2.49%

What changes are included in this PR?

• Use bulk-NULL string builders in replace

Are these changes tested?

Yes, covered by existing tests.

Are there any user-facing changes?

No.