Discover transitioned and labeled sibling targets for rust-analyzer

Summary:
When rust-analyzer resolves a Rust source file via path-based discovery (e.g. `arc rust-project develop-json '{"path":"..."}'`), Phase 1 BXL (`resolve_owning_buildfile_impl`) finds the owning target and its sibling targets in the same BUCK file. Previously, sibling discovery only matched `rust_binary|rust_library|rust_test` rule kinds. This caused failures for platform-constrained targets that rely on `transitioned()` wrappers for cross-compilation.

The failure mode:
1. Phase 1 finds the owning target (e.g. a `rust_binary` with `compatible_with` device constraints)
2. Phase 1 misses sibling `_transitioned` targets (which apply platform transitions) because they don't match the rust kind filter
3. Phase 2 (`expand_targets`) tries to configure the constrained target, but `ctx.analysis()` drops it as incompatible with the x86_64 host
4. No targets survive → empty target universe → `buck2 cquery` fails

This change makes three additions:

1. Sibling target discovery (Phase 1) now also matches `_?transitioned` rule kind, so transition wrapper targets in the same BUCK file are discovered alongside their constrained actual targets.

2. The `--buildfiles` code path gets the same `_?transitioned` kind filter plus `attrfilter("labels", "rust_analyzer_target")` for targets that opt in via label (e.g. those generated by `cli_transition_rules`).

3. Phase 2 `expand_targets` now includes `_?transitioned` in its `cquery().kind()` filter (alongside the existing `alias`), so discovered transition targets enter the configured target set. Since `_transitioned` forwards providers from its `actual` target, `RustAnalyzerInfo` is available and downstream processing works unchanged.

The `_?transitioned` regex handles both `transitioned` and `_transitioned` (the actual `buck.type` emitted by the `transitioned()` macro).

Reviewed By: dtolnay

Differential Revision: D93604237

fbshipit-source-id: fe1ea88bca70981619f154246210b5e019dd8335

Author: srv-meta

prelude/rust/rust-analyzer/resolve_deps.bxl

@@ -269,7 +269,7 @@ def expand_targets(
         targets: list[TargetLabel],
         exclude_workspaces: bool) -> (dict[Label, bxl.AnalysisResult], list[TargetLabel]):
     target_universe = ctx.target_universe(targets).target_set()
-    kind_target_list = ctx.cquery().kind("^(rust_binary|rust_library|rust_test|alias)$", target_universe)
+    kind_target_list = ctx.cquery().kind("^(rust_binary|rust_library|rust_test|alias|_?transitioned)$", target_universe)
 
     # Allow targets to opt-in to being treated as rust-analyzer-compatible.
     # This is used for cross-compilation targets that apply Buck transitions to Rust rules.
@@ -407,7 +407,9 @@ def resolve_owning_buildfile_impl(ctx: bxl.Context) -> None:
 
         # equivalent of `flat_map`ing
         targets = [target for sublist in targets for target in sublist]
-        targets = ctx.uquery().kind("^(rust_binary|rust_library|rust_test)$", targets)
+        kind_targets = ctx.uquery().kind("^(rust_binary|rust_library|rust_test|_?transitioned)$", targets)
+        labeled_targets = ctx.uquery().attrfilter("labels", "rust_analyzer_target", targets)
+        targets = kind_targets + labeled_targets
     elif ctx.cli_args.targets:
         # equivalent of `flat_map`ing
         targets = [target for sublist in ctx.cli_args.targets for target in sublist]
@@ -430,8 +432,9 @@ def resolve_owning_buildfile_impl(ctx: bxl.Context) -> None:
         if "third-party/rust/vendor/" in buildfile_path:
             continue
 
-        extra_targets = ctx.uquery().targets_in_buildfile(buildfile_path)
-        extra_targets = ctx.uquery().kind("^(rust_binary|rust_library|rust_test)$", extra_targets)
+        all_buildfile_targets = ctx.uquery().targets_in_buildfile(buildfile_path)
+        extra_targets = ctx.uquery().kind("^(rust_binary|rust_library|rust_test|_?transitioned)$", all_buildfile_targets)
+        extra_targets += ctx.uquery().attrfilter("labels", "rust_analyzer_target", all_buildfile_targets)
 
         # Exclude targets with the rustc_do_no_check label from the extra targets. This
         # label is used for foo@symbol targets (generated by rust_linkable_symbols), which