(1) Change wv_cas_ecm to allow 16 bytes of content_iv

(2) Remove "wrapping_iv" parameters from wv_cas_ecm
(3) Internally derive "wrapping_iv"s and "key_id"s
(4) Add an example binary for demo the usage of wv_cas_ecm

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=218209010

example/BUILD

@@ -16,7 +16,9 @@ package(
 filegroup(
     name = "binary_release_files",
     srcs = [
+        "wv_cas_ecm_example.cc",
         ":simulcrypt_client",
+        ":wv_cas_ecm_example",
     ],
 )
 
@@ -40,3 +42,14 @@ cc_library(
         "//base",
     ],
 )
+
+cc_binary(
+    name = "wv_cas_ecm_example",
+    srcs = ["wv_cas_ecm_example.cc"],
+    deps = [
+        "//base",
+        "@abseil_repo//absl/strings",
+        "//util:status",
+        "//media_cas_packager_sdk/public:wv_cas_ecm",
+    ],
+)