message: Switch to envoy_cc_extension.
diff: load(
  "//bazel:envoy_build_system.bzl",
  - "envoy_cc_library",
  + "envoy_cc_extension",
  "envoy_extension_package",
  )
  @@ -10,7 +10,7 @@ envoy_extension_package()
  # WASM service.
  -envoy_cc_library(
  +envoy_cc_extension(
  name = "config",
  srcs = ["config.cc"],
  hdrs = [
  