Upgrade `rand` to `0.10`, `rand_distr` to `0.6`

[Jefffrey]

Is your feature request related to a problem or challenge?

Dependabot has a PR to upgrade rand_distr:

• chore(deps): bump rand_distr from 0.5.1 to 0.6.0 #20403

This is currently blocked as it requires rand = "0.10":

• https://github.com/rust-random/rand_distr/blob/66f6791fd846ff28af51ac55d16032605a048256/CHANGELOG.md#060--2026-02-10

However it seems dependabot isn't raising a PR for rand = "0.10" because it removed a feature we use, small_rng.

Describe the solution you'd like

Manually upgrade to rand = "0.10" and rand_dist = "0.6"

datafusion/datafusion/core/Cargo.toml

Lines 175 to 176 in 89e14f1

	rand = { workspace = true, features = ["small_rng"] }
	rand_distr = "0.5"

datafusion/Cargo.toml

Line 188 in 89e14f1

rand = "0.9"

What is involved:

• Remove use of small_rng feature
  • Minimal impact (code we rely on wasn't removed, just the feature gate)
  • Reference: Remove features "nightly", "small_rng"; remove old deprecated code rust-random/rand#1732
• Replace imports of rand::Rng with rand::RngExt
  • Reference: Rename Rng => RngExt; bump rand_core to v0.10.0-rc-6 rust-random/rand#1717
• StdRng is no longer Clone, fix that somehow:
  • Reference: Remove Clone for StdRng, new bound for ReseedingRng rust-random/rand#1677

datafusion/datafusion/common/benches/with_hashes.rs

Line 238 in 89e14f1

rng.clone().sample_iter(&Alphanumeric).take(len).collect();

• Fill no longer implemented for slices
  • Reference: Let trait Fill be implemented for element types rust-random/rand#1652

datafusion/datafusion/functions/src/math/random.rs

Line 85 in 89e14f1

rng.fill(&mut values[..]);

• arrow-rs still depends on rand = "0.9" and we interface with this, so we need to upgrade arrow-rs
  • create_primitive_array comes from arrow-rs

datafusion/datafusion/functions-aggregate/benches/array_agg.rs

Line 91 in 89e14f1

let values = create_primitive_array::<T>(length, 0.0);

Describe alternatives you've considered

No response

Additional context

See changelog for rand:

• https://github.com/rust-random/rand/blob/b1ad27346a9637979c2e286988b0aa55f771ecc9/CHANGELOG.md#0100---2026-02-08

[getChan]

I took a pass at this and it looks like the remaining rough edge is arrow-rs still depending on rand 0.9 in places we interact with (for example some bench/test utilities). We can work around that locally, but that feels like the wrong direction.

I think this will be much cleaner once the relevant arrow-rs pieces are updated to rand 0.10 as well. My preference would be to defer this until then rather than add local compatibility shims/workarounds on the DataFusion side.

[Jefffrey]

It might actually be better to pin those places that depends on arrow-rs to 0.9 while we upgrade the other places, if possible. Otherwise we'd have to do these changes alongside an arrow-rs version bump.

[comphead]

Hope this would be easier than upgrade to 0.9