GS/Vulkan: Simplify loader using DynamicLibrary

Backport of https://github.com/stenzek/duckstation/commit/8e3284d8c6b28c4a73752da005e3881e6b270d10

common/Error.cpp

@@ -30,6 +30,12 @@ void Error::Clear()
 	m_description = {};
 }
 
+void Error::Clear(Error* errptr)
+{
+	if (errptr)
+		errptr->Clear();
+}
+
 void Error::SetErrno(int err)
 {
 	SetErrno(std::string_view(), err);