Convert BUILD.$name-$version.bazel to serde_starlark (#1743)
Context: see #1734.
This PR converts all of `crate_build_file.j2`, `partials/crate/*.j2` and `partials/starlark/*.j2` to serde_starlark.
### Remarks
- I kept the output of `bazel run //crate_universe/3rdparty:crates_vendor` out of this PR to keep GitHub's code review interface usable. You can find the output generated code in 44c264a7845701239e50d643b78b2bf4a117d425.
- I tried to keep the conversion 1-to-1 to the largest extent possible. As an example, build_script.j2 duplicated most of the content of common_attrs.j2 even though it probably could have used that template via include, and I have mirrored the same here by not using `#[serde(flatten)] common: CommonAttrs` inside of `CargoBuildScript`. There is probably plenty of opportunity for cleaning up things in followup PRs.
- I came across several bugs in the existing code. Again, I mostly stayed away from these to keep the PR bounded in scope. For example the fact that `rustc_flags` is stored as a BTreeSet\<String\> is not correct; compiler flags are ordered and sorting them is not correct. For example `-C debuginfo=2`...
https://github.com/bazelbuild/rules_rust/blob/532e60ff0ee3ac318333b3ae05392c220b17ce28/crate_universe/src/context/crate_context.rs#L178
- One bug that I fixed because in the new implementation it was easier to fix than to not fix, is that all existing uses of selectable_list.j2 and selectable_dict.j2 were broken because they all had the same failure mode as #1417. The generated code using `selects.with_or` could end up generating a map with duplicate keys if multiple distinct Cargo cfg expressions mapped to the same subset of supported platform triples. My implementation follows the same approach as #1647, but that PR only applied it to `deps` and `aliases`, not e.g. `rustc_env` and everything else.
- Anecdotally the new implementation has strong "if it compiles, it works" property. I mostly typed out the implementation of this PR top to bottom without running `crates_vendor`, and as soon as the whole thing was written and the compiler was okay with it, it was generating the output I wanted. I have not done much work in the templates in the past but I do not imagine they have this property.
### Remaining work
- `select_with_or` in private/selects.bzl is no longer used by the code generator's output. I had to keep it in this PR because all the generated BUILD files still include calls to it. It can be deleted after all those are regenerated.
- One of the tera templates still uses the old serialization of `SelectList` so the starlark serialization for it isn't a normal `Serialize` impl but instead an associated function. This causes there to be a bunch of `serialize_with = "SelectList::serialize_starlark"` attributes needed. This can be cleaned up after the last tera template is converted.
- ~~A lot of the contents of `crate::context` can be cleaned up after they're no longer used by tera. Tera needs those data structures to be serializable, whereas with serde_starlark we're not serializing anything from `crate::context`, only from `crate::utils::starlark`. For now I've just added a bunch of `serde(skip)` attributes in `crate::context` on all the parts tera is no longer using.~~ *Edit: apparently we still need to serialize all the fields in `Context` so that they end up in cargo-bazel-lock.json.*
- There are 2 remaining tera templates after this PR, module_bzl.j2 and vendor_module.j2.diff --git a/crate_universe/src/lib.rs b/crate_universe/src/lib.rs
index ae85717..e6fbd6f 100644
--- a/crate_universe/src/lib.rs
+++ b/crate_universe/src/lib.rs
@@ -1,3 +1,5 @@
+#![allow(clippy::large_enum_variant)]
+
pub mod cli;
mod config;
