Upgrade libsrtp to version 2.0

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index a7bcf416f884a8e2a2485cef9eb362f77d56c828..f3cf50806dfb5db53bc2454654f871392d4101ed 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -788,20 +788,6 @@ group("gn_only") {
       "//third_party/leveldatabase:leveldb_version_edit_test",
       "//third_party/leveldatabase:leveldb_write_batch_test",
       "//third_party/libjpeg_turbo:simd",
-      "//third_party/libsrtp:rdbx_driver",
-      "//third_party/libsrtp:replay_driver",
-      "//third_party/libsrtp:roc_driver",
-      "//third_party/libsrtp:rtpw",
-      "//third_party/libsrtp:srtp_driver",
-      "//third_party/libsrtp:srtp_driver",
-      "//third_party/libsrtp:srtp_test_aes_calc",
-      "//third_party/libsrtp:srtp_test_cipher_driver",
-      "//third_party/libsrtp:srtp_test_datatypes_driver",
-      "//third_party/libsrtp:srtp_test_env",
-      "//third_party/libsrtp:srtp_test_kernel_driver",
-      "//third_party/libsrtp:srtp_test_rand_gen",
-      "//third_party/libsrtp:srtp_test_sha1_driver",
-      "//third_party/libsrtp:srtp_test_stat_driver",
       "//third_party/opus:opus_compare",
       "//third_party/opus:opus_demo",
       "//third_party/opus:test_opus_api",