601: [part 1/n] Change macrotables to build.rs codegen r=lulf a=Dirbaio
This PR replaces the "macrotables" (the macros like `stm32_data::peripherals!`) with a `const METADATA`.
Macrotables had some problems:
- Hard to debug
- Somewhat footgunny (typo the "pattern" and then nothing matches and the macro now expands to nothing, silently!)
- Limited power
- Can't count, so we had to add a [special macrotable for that](f50f3f0a73/embassy-stm32/src/dma/bdma.rs (L26)).
- Can't remove duplicates, so we had to fallback to [Rust code in build.rs](f50f3f0a73/embassy-stm32/build.rs (L105-L145))
- Can't include the results as a listto another macro, so again [build.rs](https://github.com/embassy-rs/embassy/blob/master/embassy-stm32/build.rs#L100-L101).
They work fine for the 95% of cases, but for the remaining 5% we need Rust code in build.rs. So we might as well do everything with Rust code, so everything is consistent.
The new approach generates a `const METADATA: Metadata = Metadata { ... }` with [these structs](https://github.com/embassy-rs/embassy/blob/unmacrotablize/stm32-metapac-gen/src/assets/metadata.rs) in `stm32-metapac`. `build.rs` can then read that and generate whatever code.
Co-authored-by: Dario Nieuwenhuis <dirbaio@dirbaio.net>
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