Prepare v0.10.0 releases (#1729)

Minor tweaks; prepare v0.10.0-rc.9 (#1736)

@newpavlov this includes a number of what I think are uncontroversial
changes from my other PRs and also bumps versions to allow publishing a
new pre-release.

I'm not committing to keeping rand_pcg in this repo but for now this is
the easiest approach (I also wouldn't make changes here until after
v0.10).

Rename `Rng` => `RngExt`; bump `rand_core` to v0.10.0-rc-6 (#1717)

Prepare rand v0.10.0-rc.7 (#1714)

Bump versions to 0.10.0-rc.6 (#1708)

Bump rand for 0.10.0-rc.5 (#1684)

Remove rand_core and use as external dependency; bump versions to 0.1…

…0.0-rc.1 (#1678)

The next pre-releases.

Prepare 0.10.0-rc.0 (#1660)

Prepare rand 0.9.2 (#1648)

# Summary

Requested by @aleb in #1646.

## [0.9.2 — 2025-07-20]
### Deprecated
- Deprecate `rand::rngs::mock` module and `StepRng` generator (#1634)

### Additions
- Enable `WeightedIndex<usize>` (de)serialization (#1646)

Prepare rand v0.9.1 (#1629)