[bazel] Add fixes for --incompatible_load_{cc,java,proto}_rules_from_bzl (Part 2)

This change adds the required loads to examples and zlib.
For full compatibility with --incompatible_load_{cc,java,proto}_rules_from_bzl,
we will need to roll gtest to a newer version.

protobuf_deps.bzl

diff --git a/protobuf_deps.bzl b/protobuf_deps.bzl
index 57509ee..ffa5d0a 100644
--- a/protobuf_deps.bzl
+++ b/protobuf_deps.bzl
@@ -5,6 +5,14 @@
 def protobuf_deps():
     """Loads common dependencies needed to compile the protobuf library."""
 
+    if not native.existing_rule("bazel_skylib"):
+        http_archive(
+            name = "bazel_skylib",
+            sha256 = "bbccf674aa441c266df9894182d80de104cabd19be98be002f6d478aaa31574d",
+            strip_prefix = "bazel-skylib-2169ae1c374aab4a09aa90e65efe1a3aad4e279b",
+            urls = ["https://github.com/bazelbuild/bazel-skylib/archive/2169ae1c374aab4a09aa90e65efe1a3aad4e279b.tar.gz"],
+        )
+
     if not native.existing_rule("zlib"):
         http_archive(
             name = "zlib",