printf: Fix floating-point rounding consistency for RTZ devices (#2202)

1. In vector test, prepare RTZ answer for RTZ rounding.

2. In mixed_format_random test, for a given float 'arg', the test
previously used 'arg' directly to generate ref_str:
   ```
     ref_str << str_sprintf(format, arg);
   ```

   This approach incorrectly assumes:
   ```
     (float) arg == to_fp(to_str(arg));
   ```

   However, this assumption fails under RTZ rounding. For example: 
   ```
     arg = 0xC642549C 
     to_str(arg) = -12437.152343f 
     to_fp_rtz(-12437.152343f) = 0xC642549B (-0X1.84A936P+13) 
     to_fp_rte(-12437.152343f) = 0xC642549C (-0X1.84A938P+13)
   ```

To address this, the reference result is now computed based on the
literal float string rather than the original 'arg' value.

test_conformance/printf/test_printf.cpp

@@ -317,8 +317,10 @@ cl_program makeMixedFormatPrintfProgram(cl_kernel* kernel_ptr,
         {
             const float max_range = 100000.f;
             float arg = get_random_float(-max_range, max_range, gMTdata);
-            args_str << str_sprintf("%f", arg) << "f, ";
-            ref_str << str_sprintf(format, arg) << ", ";
+            std::string arg_str = str_sprintf("%f", arg);
+            args_str << arg_str << "f, ";
+            float arg_deviceRound = std::stof(arg_str);
+            ref_str << str_sprintf(format, arg_deviceRound) << ", ";
         }
     }
     // Restore the original CPU rounding mode

test_conformance/printf/util_printf.cpp

@@ -1336,6 +1336,33 @@ std::vector<std::string> correctBufferVector = {
     "00512,01024,262144,1048576"
 };
 
+std::vector<std::string> correctBufferVectorRTZ = {
+
+    "1.00,2.00,3.00,4.00",
+
+    "0xfa,0xfb",
+
+    "0x1234,0x8765",
+
+    "0x12345678,0x87654321",
+
+    "12345678,98765432",
+
+    "1.00,2.00,3.00,4.00",
+
+    "1.23e+03,9.87e+05,4.99e-04",
+
+    "0x1p-2,0x1p-1,0x1p+0,0x1.8p+0",
+
+    "1,2,3,4,1.5,3.13999,2.5,3.5",
+
+    "1,2,3,4,5,6,7,10,11,0,40,100,200,400,1000,2000",
+
+    "+1,-2,+3,-4,+5,-6,+7,-8",
+
+    "00512,01024,262144,1048576"
+};
+
 //-----------------------------------------------------------
 
 //Test case for vector                                      |
@@ -1822,7 +1849,14 @@ void generateRef(const cl_device_id device)
             as they're constant and hard-coded
         */
         if (caseToTest->printFN == NULL)
+        {
+            if (caseToTest->_type == TYPE_VECTOR
+                && fpConfigSingle == CL_FP_ROUND_TO_ZERO)
+            {
+                caseToTest->_correctBuffer = correctBufferVectorRTZ;
+            }
             continue;
+        }
 
         // Make sure the reference result is empty
         assert(caseToTest->_correctBuffer.size() == 0);