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

commit_hash:7a4a1c6d6ddbe60d686f292315d468848326ab1f

Author: maxim-babenko

yt/yt/library/quantile_digest/quantile_digest.cpp

@@ -45,7 +45,7 @@ class TTDigestAdaptor
         return UnderlyingDigest_.GetRank(value);
     }
 
-    TString Serialize() override
+    std::string Serialize() override
     {
         NProto::TQuantileDigest quantileDigest;
 

yt/yt/library/quantile_digest/quantile_digest.h

@@ -17,7 +17,7 @@ struct IQuantileDigest
 
     virtual double GetRank(double value) = 0;
 
-    virtual TString Serialize() = 0;
+    virtual std::string Serialize() = 0;
 
     virtual void MergeWith(const IQuantileDigestPtr& other) = 0;
 };