Added granular interfaces for core rules (#3402)

This matches what we see in other rules.

Author: UebelAndre

rust/rust_binary.bzl

@@ -0,0 +1,8 @@
+"""rust_binary"""
+
+load(
+    "//rust/private:rust.bzl",
+    _rust_binary = "rust_binary",
+)
+
+rust_binary = _rust_binary

rust/rust_library.bzl

@@ -0,0 +1,8 @@
+"""rust_library"""
+
+load(
+    "//rust/private:rust.bzl",
+    _rust_library = "rust_library",
+)
+
+rust_library = _rust_library

rust/rust_library_group.bzl

@@ -0,0 +1,8 @@
+"""rust_library_group"""
+
+load(
+    "//rust/private:rust.bzl",
+    _rust_library_group = "rust_library_group",
+)
+
+rust_library_group = _rust_library_group

rust/rust_proc_macro.bzl

@@ -0,0 +1,8 @@
+"""rust_proc_macro"""
+
+load(
+    "//rust/private:rust.bzl",
+    _rust_proc_macro = "rust_proc_macro",
+)
+
+rust_proc_macro = _rust_proc_macro

rust/rust_shared_library.bzl

@@ -0,0 +1,8 @@
+"""rust_shared_library"""
+
+load(
+    "//rust/private:rust.bzl",
+    _rust_shared_library = "rust_shared_library",
+)
+
+rust_shared_library = _rust_shared_library

rust/rust_static_library.bzl

@@ -0,0 +1,8 @@
+"""rust_static_library"""
+
+load(
+    "//rust/private:rust.bzl",
+    _rust_static_library = "rust_static_library",
+)
+
+rust_static_library = _rust_static_library

rust/rust_test.bzl

@@ -0,0 +1,8 @@
+"""rust_test"""
+
+load(
+    "//rust/private:rust.bzl",
+    _rust_test = "rust_test",
+)
+
+rust_test = _rust_test