Set bls_lagrange rand dependency to workspace.

[gnattishness]

Update to [email protected] and replace deprecated names.

Issue Addressed

Fixes #461

Proposed Changes

Use rand 0.9 and set to workspace version.

Additional Info

Its a very small change, understandable if you don't want to accept it :)

[cla-assistant]

All committers have signed the CLA.

[Copilot]

Pull Request Overview

This PR updates the bls_lagrange crate to use [email protected] by setting the dependency to workspace version and replacing deprecated method names with their current equivalents.

• Updates rand dependency from hardcoded "0.8.5" to workspace version
• Replaces deprecated thread_rng() with rand::rng()
• Updates deprecated method names: gen() → random(), gen_range() → random_range()

Reviewed Changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
anchor/common/bls_lagrange/Cargo.toml	Updates rand dependency to use workspace version
anchor/common/bls_lagrange/src/lib.rs	Replaces deprecated rand method names with current equivalents

Comments suppressed due to low confidence (5)

anchor/common/bls_lagrange/src/lib.rs:30

• The function rand::rng() does not exist in rand 0.9. The correct replacement for thread_rng() is rand::thread_rng().

    split_with_rng(key, threshold, ids, &mut rand::rng())

anchor/common/bls_lagrange/src/lib.rs:35

• The method random() does not exist on RNG traits in rand 0.9. The correct method name is gen(), which remains unchanged from rand 0.8.

    let ikm = zeroize::Zeroizing::new(rng.random::<[u8; 32]>());

anchor/common/bls_lagrange/src/lib.rs:60

• The method random_range() does not exist on RNG traits in rand 0.9. The correct method name is gen_range(), which remains unchanged from rand 0.8.

        let total = rng.random_range(2..=13);

anchor/common/bls_lagrange/src/lib.rs:61

• The method random_range() does not exist on RNG traits in rand 0.9. The correct method name is gen_range(), which remains unchanged from rand 0.8.

        let threshold = rng.random_range(2..=total);

anchor/common/bls_lagrange/src/lib.rs:84

• The method random_range() does not exist on RNG traits in rand 0.9. The correct method name is gen_range(), which remains unchanged from rand 0.8.

        let signers = rng.random_range(2..=total);

[dknopik]

This breaks when building with feature = blsful, as we pass the RNG to a dependency which still uses rand 0.8.

However, we have been using the custom blst variant for a while now and I am open to just removing the blsful variant. Then we could merge this.

[gnattishness]

Ah thanks! I'd not checked with the blsful feature.
I'll have a bit of a play around and get back to you. If feasible to maintain, having the variant (which is supposed to be equivalent) seems helpful to test correctness