rust_test_suite: ensure crate names are valid (#1248)

I noticed this while setting up rust_test_suite auto-generation at
work. Seems like a simple enough fix.

Co-authored-by: Augie Fackler <augie@google.com>
diff --git a/rust/private/rust.bzl b/rust/private/rust.bzl
index af11c9f..dfef5c8 100644
--- a/rust/private/rust.bzl
+++ b/rust/private/rust.bzl
@@ -23,6 +23,7 @@
     "expand_dict_value_locations",
     "find_toolchain",
     "get_import_macro_deps",
+    "name_to_crate_name",
     "transform_deps",
 )
 
@@ -1179,7 +1180,7 @@
         test_name = name + "_" + src[:-3]
         rust_test(
             name = test_name,
-            crate_name = test_name.replace("/", "_"),
+            crate_name = name_to_crate_name(test_name.replace("/", "_")),
             srcs = [src],
             **kwargs
         )