tests: Add test for builtin help function.

tests/basics/builtin_help.py

+# test builtin help function
+
+try:
+    help
+except NameError:
+    print("SKIP")
+    import sys
+    sys.exit()
+
+help() # no args
+help(help) # help for a function
+help(int) # help for a class
+help(1) # help for an instance
+import micropython
+help(micropython) # help for a module
+
+print('done') # so last bit of output is predictable

tests/basics/builtin_help.py.exp

+########
+object <function> is of type function
+object <class 'int'> is of type type
+  from_bytes -- <classmethod>
+  to_bytes -- <function>
+object 1 is of type int
+  from_bytes -- <classmethod>
+  to_bytes -- <function>
+object <module 'micropython'> is of type module
+  __name__ -- micropython
+  const -- <function>
+  opt_level -- <function>
+########
+done

tests/run-tests

@@ -51,7 +51,7 @@ def convert_regex_escapes(line):
 
 
 def run_micropython(pyb, args, test_file):
-    special_tests = ('micropython/meminfo.py', 'basics/bytes_compare3.py', 'thread/thread_exc2.py')
+    special_tests = ('micropython/meminfo.py', 'basics/bytes_compare3.py', 'basics/builtin_help.py', 'thread/thread_exc2.py')
     is_special = False
     if pyb is None:
         # run on PC