Automatic toolchain upgrade to nightly-2026-01-02

[github-actions]

Update Rust toolchain from nightly-2026-01-01 to nightly-2026-01-02 without any other source changes.

[github-actions]

This is an automatically generated pull request. If any of the CI checks fail,
manual intervention is required. In such a case, review the changes at
https://github.com/rust-lang/rust from
rust-lang/rust@8d670b9 up to
rust-lang/rust@fcd6309. The log
for this commit range is:

https://github.com/rust-lang/rust/commit/fcd630976c Auto merge of #150565 - RalfJung:miri, r=RalfJung

rust-lang/rust@cc08b553b8 Auto merge of #150563 - JonathanBrouwer:rollup-9ncjbou, r=JonathanBrouwer
rust-lang/rust@cef03a789a Rollup merge of #150529 - rustbot:docs-update, r=ehuss
rust-lang/rust@36457ce8f9 Rollup merge of #150454 - tiif:move_variadic, r=oli-obk
rust-lang/rust@b49c7d784e Auto merge of #150523 - Kivooeo:add-check-for-u8, r=BoxyUwU
rust-lang/rust@6e48b44e77 Auto merge of #150559 - JonathanBrouwer:rollup-59hbbmm, r=JonathanBrouwer
rust-lang/rust@767e7dae25 Rollup merge of #150555 - adamgreig:armv7-thumb-interwork, r=chenyukang
rust-lang/rust@f5803f0610 Rollup merge of #150548 - dianne:temp-scope-extension-loop-rewrite, r=BoxyUwU
rust-lang/rust@71b17c5c18 Rollup merge of #150264 - RalfJung:target-feature-tracking-split, r=Amanieu
rust-lang/rust@9b89b8814a Rollup merge of #149778 - tbu-:pr_crate_io_result, r=Mark-Simulacrum
rust-lang/rust@4c62aa4468 Auto merge of #150520 - malbarbo:case_get_unchecked, r=jhpratt
rust-lang/rust@48622726c4 Auto merge of #150289 - rami3l:dist/rustc-docs-dist-path, r=jieyouxu