Moving functions that use protocol buffers to "testing/proto_utils" from testing/utils. This CL does not add any new code and only touches test and build files.

All the other files in this CL have changes related to adding "testing/proto_utils" as a dependency instead of / in addition to "testing/utils".

Tldr; Splits an existing file into two and adds the paths for the second file in all relevant BUILD, header and cc files.

PiperOrigin-RevId: 539760965
diff --git a/build/source_list.json b/build/source_list.json
index ae24505..f30cdfa 100644
--- a/build/source_list.json
+++ b/build/source_list.json
@@ -1571,6 +1571,7 @@
     "quiche/blind_sign_auth/anonymous_tokens/cpp/crypto/verifier.h",
     "quiche/blind_sign_auth/anonymous_tokens/cpp/shared/proto_utils.h",
     "quiche/blind_sign_auth/anonymous_tokens/cpp/shared/status_utils.h",
+    "quiche/blind_sign_auth/anonymous_tokens/cpp/testing/proto_utils.h",
     "quiche/blind_sign_auth/anonymous_tokens/cpp/testing/utils.h",
     "quiche/blind_sign_auth/blind_sign_auth.h",
     "quiche/blind_sign_auth/blind_sign_auth_interface.h",
@@ -1587,6 +1588,7 @@
     "quiche/blind_sign_auth/anonymous_tokens/cpp/crypto/rsa_blinder.cc",
     "quiche/blind_sign_auth/anonymous_tokens/cpp/crypto/rsa_ssa_pss_verifier.cc",
     "quiche/blind_sign_auth/anonymous_tokens/cpp/shared/proto_utils.cc",
+    "quiche/blind_sign_auth/anonymous_tokens/cpp/testing/proto_utils.cc",
     "quiche/blind_sign_auth/anonymous_tokens/cpp/testing/utils.cc",
     "quiche/blind_sign_auth/blind_sign_auth.cc",
     "quiche/blind_sign_auth/cached_blind_sign_auth.cc"