YT-22593: Migrate TString to std::string in yt/yt/library/auth

commit_hash:6220afa4e52e00df3faddb6a2fc687fe92e1962c

Author: maxim-babenko

yt/yt/library/auth/credentials_injecting_channel.cpp

@@ -119,7 +119,7 @@ class TTokenInjectingChannel
     }
 
 private:
-    const TString Token_;
+    const std::string Token_;
 };
 
 IChannelPtr CreateTokenInjectingChannel(
@@ -158,8 +158,8 @@ class TCookieInjectingChannel
     }
 
 private:
-    const TString SessionId_;
-    const TString SslSessionId_;
+    const std::string SessionId_;
+    const std::string SslSessionId_;
 };
 
 IChannelPtr CreateCookieInjectingChannel(
@@ -233,7 +233,7 @@ class TUserTicketInjectingChannel
     }
 
 private:
-    const TString UserTicket_;
+    const std::string UserTicket_;
 };
 
 NRpc::IChannelPtr CreateUserTicketInjectingChannel(