Merge #601

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>

embassy-stm32/Cargo.toml

@@ -36,7 +36,9 @@ seq-macro = "0.2.2"
 cfg-if = "1.0.0"
 
 [build-dependencies]
-stm32-metapac = { version = "0.1.0", path = "../stm32-metapac", default-features = false }
+proc-macro2 = "1.0.36"
+quote = "1.0.15"
+stm32-metapac = { version = "0.1.0", path = "../stm32-metapac", default-features = false, features = ["metadata"]}
 
 [features]
 sdmmc-rs = ["embedded-sdmmc"]