ci: update preview build to Rust 1.90.0

[zemaj]

Summary

• bump the preview workflow to Rust 1.90.0 across Linux, macOS, and Windows runners
• add an explicit rustup target add for each matrix target and ensure both musl targets are installed on Linux jobs
• update rust-cache keys to match the new toolchain version while keeping the publish job gating introduced in fix(ci): skip publish job on fork PRs to prevent permission failures #359 untouched

Fixes #357
Fixes #358
Fixes #362
Fixes #363

Testing

• ./build-fast.sh (1.90.0)

[zemaj]

Requesting merge: this bumps preview-build to Rust 1.90.0 and installs both musl targets on Linux jobs, unblocking the failures on #357, #358, #362, and #363.

[zemaj]

All preview-build checks are green on #364. Could we merge this to unblock the E0463 failures on #357, #358, #362, and #363? I've got reruns queued to fire the moment it lands.