feat: add d_proto_library

[dcarp]

Summary

Adds d_proto_library for generating and compiling D code from proto_library targets.

This uses Protobuf’s Bazel-provided ProtoInfo and protoc, plus the protobuf-d v0.7.0 runtime/compiler plugin exposed as @protobuf_d. The rule follows the modern <lang>_proto_library shape where proto inputs are provided through deps.

Changes

• Add d_proto_library and d_proto_aspect
• Generate D sources with @protobuf//:protoc and @protobuf_d//protoc_gen_d:protoc-gen-d
• Compile generated D sources through the shared d_compile helper
• Add protobuf 30.2 and protobuf_d repository setup for Bzlmod and WORKSPACE
• Refactor d_compile/d_proto_compile to take explicit action inputs instead of full rule context
• Add in-repo proto coverage, including transitive proto deps
• Add e2e smoke coverage for d_proto_library in both Bzlmod and WORKSPACE setup

Testing

• bazel test //...
• bazel test //... from e2e/smoke
• USE_BAZEL_VERSION=8.4.2 bazel --output_base=/tmp/rules_d_e2e_workspace_bazel_8_4_2 test //... --enable_workspace --noenable_bzlmod