Update to a more recent rules rust and update to use defs.bzl

Rules rust has made some changes upstream that remove the rust.bzl file.
It had previously been left in there for compatibility purposes.  This
has been ongoing since February 16th.  See this issue for additional
context: bazelbuild/rules_rust#591.

WORKSPACE

@@ -333,11 +333,11 @@ _go_image_repos()
 # For our rust_image test
 http_archive(
     name = "rules_rust",
-    sha256 = "42e60f81e2b269d28334b73b70d02fb516c8de0c16242f5d376bfe6d94a3509f",
-    strip_prefix = "rules_rust-58f709ffec90da93c4e622d8d94f0cd55cd2ef54",
+    sha256 = "d6a8bc37502f252ef190b37945c922e0d0104dc2250940a3ea5f9c42e7a0dc10",
+    strip_prefix = "rules_rust-e2f0fccda912daac686b533ad77c5bc5d2f2ddb7",
     urls = [
-        # Master branch as of 2021-02-04
-        "https://github.com/bazelbuild/rules_rust/archive/58f709ffec90da93c4e622d8d94f0cd55cd2ef54.tar.gz",
+        # `main` branch as of 2021-11-05
+        "https://github.com/bazelbuild/rules_rust/archive/e2f0fccda912daac686b533ad77c5bc5d2f2ddb7.tar.gz",
     ],
 )
 

rust/image.bzl

@@ -16,7 +16,7 @@
 The signature of this rule is compatible with rust_binary.
 """
 
-load("@rules_rust//rust:rust.bzl", "rust_binary")
+load("@rules_rust//rust:defs.bzl", "rust_binary")
 load(
     "//cc:image.bzl",
     "DEFAULT_BASE",