ci(proto): preserve historical paths to avoid spurious semver findings

The Apache/datafusion CI's `Comment on pull request` job posts semver-check
findings as a PR comment via bash; with the volume of cross-crate re-exports
in this PR, the comment body blew past `Argument list too long`.

Two source-level changes shrink the findings list:

- Re-export the `datafusion_common` package types from inside
  `proto-models::generated::datafusion` so historical paths like
  `datafusion_proto::generated::datafusion::JoinType` keep resolving.
  Pre-change, those types were embedded duplicates inside the proto crate's
  `mod datafusion`; after the absorb in C2 they only lived under the common
  package mod, which cargo-semver-checks flagged as "removed".
- Add a `pbjson` feature alias on `datafusion-proto` that forwards to `json`.
  Pre-change, `pbjson` was an optional dep, which auto-created a `pbjson`
  feature; consumers depending on `datafusion-proto/pbjson` would otherwise
  break.

No runtime behavior change.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: adriangb

datafusion/proto-models/src/generated/mod.rs

@@ -36,6 +36,11 @@ pub mod datafusion_proto_common {
 pub mod datafusion {
     include!("datafusion.rs");
 
+    // Re-export the `datafusion_common` package types from inside `mod datafusion`
+    // so historical paths like `datafusion_proto::generated::datafusion::JoinType`
+    // (which used to be embedded duplicates of the common types) keep resolving.
+    pub use super::datafusion_proto_common::*;
+
     #[cfg(feature = "json")]
     include!("datafusion.serde.rs");
 }

datafusion/proto/Cargo.toml

@@ -37,6 +37,12 @@ name = "datafusion_proto"
 [features]
 default = ["parquet"]
 json = ["serde_json", "datafusion-proto-models/json"]
+# Back-compat alias: pbjson used to be an optional dep auto-creating a `pbjson`
+# feature. After the proto-models extraction, datafusion-proto no longer has a
+# direct pbjson dep; the JSON serde plumbing forwards through proto-models.
+# Keep `pbjson` as a feature alias for `json` so downstream `features = ["pbjson"]`
+# continues to work.
+pbjson = ["json"]
 parquet = ["datafusion-datasource-parquet", "datafusion-common/parquet", "datafusion/parquet"]
 avro = ["datafusion-datasource-avro"]