Add preprocessing for CProverString.format

This makes the link between the CProverString.format signature from java
and the ID_cprover_string_format_func from the solver.

Author: romainbrenguier

jbmc/src/java_bytecode/java_string_library_preprocess.cpp

@@ -1858,6 +1858,14 @@ void java_string_library_preprocesst::initialize_conversion_table()
         std::placeholders::_2,
         std::placeholders::_3,
         std::placeholders::_4);
+
+  std::string format_signature = "java::org.cprover.CProverString.format:(";
+  for(std::size_t i = 0; i < MAX_FORMAT_ARGS + 1; ++i)
+    format_signature += "Ljava/lang/String;";
+  format_signature += ")Ljava/lang/String;";
+  cprover_equivalent_to_java_string_returning_function[format_signature] =
+      ID_cprover_string_format_func;
+
   cprover_equivalent_to_java_function
     ["java::java.lang.String.hashCode:()I"]=
       ID_cprover_string_hash_code_func;