Rename all BUILD files to BUILD.bazel (#9892)

This avoids conflicting names in a couple of cases.

1. Within google, we want to sync files but not name them BUILD (since the structure doesn't match).
2. On case-insensitive filesystems, `build` may be used for a build directory. Naming `BUILD.bazel` avoids potentioal conflicts.
diff --git a/java/internal/BUILD.bazel b/java/internal/BUILD.bazel
new file mode 100644
index 0000000..662dabd
--- /dev/null
+++ b/java/internal/BUILD.bazel
@@ -0,0 +1,13 @@
+package(default_visibility = ["//java:__subpackages__"])
+
+load("@rules_pkg//:mappings.bzl", "pkg_files", "strip_prefix")
+
+pkg_files(
+    name = "dist_files",
+    srcs = [
+        "BUILD.bazel",
+        "testing.bzl",
+    ],
+    strip_prefix = strip_prefix.from_root(""),
+    visibility = ["//java:__pkg__"],
+)