Rename report_result.cpp -> report_result.c. NFC (#16148)

It doesn't contain any C++ code.

Author: sbc100

tests/common.py

@@ -1549,10 +1549,10 @@ def compile_btest(self, args, reporting=Reporting.FULL):
                '--pre-js', test_file('browser_reporting.js')]
       if reporting == Reporting.FULL:
         # If C reporting (i.e. REPORT_RESULT macro) is required
-        # also compile in report_result.cpp and forice-include report_result.h
+        # also compile in report_result.c and forice-include report_result.h
         args += ['-I' + TEST_ROOT,
                  '-include', test_file('report_result.h'),
-                 test_file('report_result.cpp')]
+                 test_file('report_result.c')]
     if EMTEST_BROWSER == 'node':
       args.append('-DEMTEST_NODE')
     self.run_process([EMCC] + self.get_emcc_args() + args)

tests/report_result.cpp renamed to tests/report_result.c

@@ -7,6 +7,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdbool.h>
 
 #include "report_result.h"