Applied some cppcheck [useStlAlgorithm] recommendations. (#1924)

* Use copy_if instead of raw loop.

* Replaced for loop with std::any_of.

Author: Dimi1010

Packet++/src/Asn1Codec.cpp

@@ -612,12 +612,9 @@ namespace pcpp
 			throw std::invalid_argument("Value is not a valid hex stream");
 		}
 
-		for (const char i : valueStr)
+		if (std::any_of(valueStr.begin(), valueStr.end(), [](char c) { return !std::isxdigit(c); }))
 		{
-			if (!std::isxdigit(i))
-			{
-				throw std::invalid_argument("Value is not a valid hex stream");
-			}
+			throw std::invalid_argument("Value is not a valid hex stream");
 		}
 
 		return valueStr;

Packet++/src/SmtpLayer.cpp

@@ -44,13 +44,8 @@ namespace pcpp
 		}
 
 		std::string optionWithEscapeChars;
-		for (char ch : option)
-		{
-			if (ch < 127 && ch > 31)
-			{
-				optionWithEscapeChars.push_back(ch);
-			}
-		}
+		std::copy_if(option.begin(), option.end(), std::back_inserter(optionWithEscapeChars),
+		             [](char ch) { return ch < 127 && ch > 31; });
 
 		return optionWithEscapeChars;
 	}