bump rand_core version to 0.9.0

[John-Vash]

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Submission Checklist 📝

• I have updated existing examples or added new ones (if applicable).
• I have used cargo xtask fmt-packages command to ensure that all changed code is formatted correctly.
• My changes were added to the CHANGELOG.md in the proper section.
• I have added necessary changes to user code to the Migration Guide.
• My changes are in accordance to the esp-rs API guidelines

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• I have read the CONTRIBUTING.md guide and followed its instructions.

Pull Request Details 📖

Description

Please provide a clear and concise description of your changes, including the motivation behind these changes. The context is crucial for the reviewers.

These changes are to support the latest version of rand_core's RngCore trait, where try_fill_bytes has been moved to the TryRngCore trait.

Testing

Describe how you tested your changes.

Tested by running wifi examples where a u64 seed is generated via RngCore::next_u64 on a esp32-c6 devkit.

[SergioGasquez]

I guess this deserves a mention in the migration guide.

[bugadani]

We shouldn't unconditionally pull in <1.0 dependencies, even if the RNG itself is unstable.

[jessebraham]

We shouldn't unconditionally pull in <1.0 dependencies, even if the RNG itself is unstable.

What do you mean by this? This dependency was already included, they've just updated the version, and there are like a dozen other dependencies which are <1.0 and not behind a feature.

[bugadani]

RngCore will be part of our public API. By the way, is there a reason to actually drop support for the old version?

[John-Vash]

I have added an entry to the MIGRATING-0.23.md document.

Also just to clarify a bit, the removal of esp-hal's try_fill_bytes implementation does not mean the try_fill_bytes method has been removed from esp-hal::rng::Rng completely. With the latest update to rand_core, an implementation of the RngCore trait auto implements the TryRngCore trait and the try_fill_bytes method exists as part of the TryRngCore trait. This means esp-hal::rng::Rng still provides the try_fill_bytes method when the rand_core::TryRngCore trait is in scope.