Move Bazel workspace root, refactor BUILD files, and add aliases

- Moved Bazel workspace files (MODULE.bazel, WORKSPACE.bazel, .bazelrc, etc.) from `proto/` to the repository root.
- Refactored `proto/BUILD.bazel` by splitting targets into colocated BUILD files in `proto/p4/config/v1/BUILD.bazel` and `proto/p4/v1/BUILD.bazel`.
- Added `strip_import_prefix = "/proto"` to proto_library targets.
- Added aliases in the root `BUILD.bazel` to maintain backward compatibility for users who update their workspace root.
- Added aliases in `proto/BUILD.bazel` to maintain backward compatibility for users who do not update their workspace root (though strictly speaking the paths are different).
- Updated example projects to use the new canonical targets and workspace root.

Fixes #571.

Author: google-labs-jules[bot]

BUILD.bazel

@@ -1 +1,41 @@
+load("@bazel_skylib//rules:build_test.bzl", "build_test")
+load("@rules_license//rules:license.bzl", "license")
+
+package(
+    default_visibility = ["//visibility:public"],
+    default_applicable_licenses = [":license"],
+)
+
+license(
+    name = "license",
+    license_kinds = ["@rules_license//licenses/spdx:Apache-2.0"],
+    license_text = "LICENSE",
+)
+
 exports_files(["LICENSE", "p4runtime_deps.bzl"])
+
+# Aliases for backward compatibility with the old workspace structure
+# where proto/ was the root.
+
+alias(name = "p4types_proto", actual = "//proto/p4/config/v1:p4types_proto")
+alias(name = "p4info_proto", actual = "//proto/p4/config/v1:p4info_proto")
+alias(name = "p4data_proto", actual = "//proto/p4/v1:p4data_proto")
+alias(name = "p4runtime_proto", actual = "//proto/p4/v1:p4runtime_proto")
+
+alias(name = "p4types_cc_proto", actual = "//proto/p4/config/v1:p4types_cc_proto")
+alias(name = "p4info_cc_proto", actual = "//proto/p4/config/v1:p4info_cc_proto")
+alias(name = "p4data_cc_proto", actual = "//proto/p4/v1:p4data_cc_proto")
+alias(name = "p4runtime_cc_proto", actual = "//proto/p4/v1:p4runtime_cc_proto")
+
+alias(name = "p4types_py_proto", actual = "//proto/p4/config/v1:p4types_py_proto")
+alias(name = "p4info_py_proto", actual = "//proto/p4/config/v1:p4info_py_proto")
+alias(name = "p4data_py_proto", actual = "//proto/p4/v1:p4data_py_proto")
+alias(name = "p4runtime_py_proto", actual = "//proto/p4/v1:p4runtime_py_proto")
+
+alias(name = "p4info_go_proto", actual = "//proto/p4/config/v1:p4info_go_proto")
+alias(name = "p4runtime_go_proto", actual = "//proto/p4/v1:p4runtime_go_proto")
+
+alias(name = "p4runtime_cc_grpc", actual = "//proto/p4/v1:p4runtime_cc_grpc")
+alias(name = "p4runtime_py_grpc", actual = "//proto/p4/v1:p4runtime_py_grpc")
+
+test_suite(name = "proto_build_test", tests = ["//proto:proto_build_test"])