chore: increase row count and batch size for more deterministic tests

[Weijun-H]

Which issue does this PR close?

• Closes #NNN.

Rationale for this change

Previous benchmark is too fast to deterministically measure the performance improvement because they run only in 2-7 microsecond.

What changes are included in this PR?

Are these changes tested?

Are there any user-facing changes?

[Jefffrey]

After these changes on an M4 mac

arrow-rs (pr_9088)$ cargo bench -p arrow-json
    Finished `bench` profile [optimized] target(s) in 0.05s
     Running benches/serde.rs (/Users/jeffrey/.cargo_target_cache/release/deps/serde-a1ab5d1498b8bdfe)
small_i32               time:   [323.29 µs 325.91 µs 328.65 µs]
Found 6 outliers among 100 measurements (6.00%)
  1 (1.00%) low mild
  5 (5.00%) high mild

Benchmarking large_i32: Collecting 100 samples in estimated 6.5412 s (20k iterations)^C⏎                                                                                                                              arrow-rs (pr_9088)$ cargo bench -p arrow-json --bench serde
    Finished `bench` profile [optimized] target(s) in 0.06s
     Running benches/serde.rs (/Users/jeffrey/.cargo_target_cache/release/deps/serde-a1ab5d1498b8bdfe)
small_i32               time:   [314.67 µs 315.97 µs 317.47 µs]
                        change: [−2.6760% −1.8315% −0.9768%] (p = 0.00 < 0.05)
                        Change within noise threshold.
Found 10 outliers among 100 measurements (10.00%)
  6 (6.00%) high mild
  4 (4.00%) high severe

large_i32               time:   [315.96 µs 317.31 µs 318.82 µs]
Found 3 outliers among 100 measurements (3.00%)
  2 (2.00%) high mild
  1 (1.00%) high severe

small_i64               time:   [483.97 µs 485.09 µs 486.20 µs]
Found 2 outliers among 100 measurements (2.00%)
  2 (2.00%) high severe

medium_i64              time:   [485.07 µs 487.39 µs 491.23 µs]
Found 5 outliers among 100 measurements (5.00%)
  2 (2.00%) high mild
  3 (3.00%) high severe

large_i64               time:   [486.93 µs 491.01 µs 498.46 µs]
Found 2 outliers among 100 measurements (2.00%)
  2 (2.00%) high severe

small_f32               time:   [575.10 µs 578.78 µs 585.47 µs]
Found 3 outliers among 100 measurements (3.00%)
  1 (1.00%) low mild
  1 (1.00%) high mild
  1 (1.00%) high severe

large_f32               time:   [572.65 µs 573.71 µs 574.81 µs]
Found 1 outliers among 100 measurements (1.00%)
  1 (1.00%) low mild

[alamb]

Thanks @Weijun-H and @Jefffrey