polyfill for `cfg_select` does not emit the same code

### Bug Description The `cfg_select` macro in `core` selects the first branch that evaluates to true and ignores all the rest. The polyfill selects _all_ the branches that evaluate to true. ### Steps to Reproduce - write a `cfg_select` with multiple branches that have predicates that evaluate to true - expand it (use IDE or cargo expand) - set rust toolchain to 1.83 and expand it again ### Backtrace ```shell ``` ### Your operating system and version . ### Your Python version (`python --version`) . ### Your Rust version (`rustc --version`) . ### Your PyO3 version . ### How did you install python? Did you use a virtualenv? . ### Additional Info _No response_