Tracking issue for v0.4 release

[newpavlov]

List of potential breaking changes:

• Bump MSRV to 1.85 and edition to 2024
• Relax MSRV policy to allow MSRV bumps in patch releases, i.e. we would rely on the MSRV-aware resolver going forward
• Remove the wasm_js backend in favor of the custom fallback crate feature (also see Add feature-gated getrandom support wasm-bindgen/wasm-bindgen#4667)

It's arguably a good time to synchronize v0.4 release with the planned rand v0.10 release (which also bumps MSRV to 1.85).