Demoting i686 Windows targets to std-only
Summary
Rust 1.100.0 introduces changes to 32-bit Windows targets: i686-pc-windows-msvc will be demoted to a host-tools-free Tier 1, and i686-pc-windows-gnu to Tier 2 without host tools. The standard library will still be distributed, but host tools like the compiler will no longer be available; cross-compiling from a supported host (e.g., 64-bit Windows) will be required. The change reflects the end-of-life for 32-bit Windows development platforms and aims to simplify maintenance.