Rework the public API (#4829)

Related to #4186.

Some notable changes:
  - The term 'Error' now strictly refers to native Error objects defined in
    the ECMA standard, which are ordinary objects. All other uses of
    'error' or 'error reference' where the term refers to a thrown value is
    now called 'exception'.

  - Simplified the naming scheme of many String API functions. These functions
    will now also take an 'encoding' argument to specify the desired
    encoding in which to operate.

  - Removed the substring-copy-to-buffer functions. These functions
    behaved awkwardly, as they use character index to specify the
    start/end positions, and were mostly used incorrectly with byte
    offsets instead. The functionality can still be replicated with
    other functions if necessary.

  - String-to-buffer functions will no longer fail if the buffer is not
    sufficiently large, the string will instead be cropped.

  - Fixed the usage of the '_sz' prefix in many API functions. The term
    'sz' means zero-terminated string in hungarian notation, this was
    used incorrectly in many cases.

  - Renamed most of the public API functions to have shorter, more on-point
    names, rather than the often too long descriptive names. Functions are now
    also grouped by the type of value they operate on, where this makes
    sense.

JerryScript-DCO-1.0-Signed-off-by: Dániel Bátyai dbatyai@inf.u-szeged.hu

jerry-ext/arg/arg.c

@@ -35,11 +35,11 @@ jerryx_arg_transform_args (const jerry_value_t *js_arg_p, /**< points to the arr
                            const jerryx_arg_t *c_arg_p, /**< points to the array of validation/transformation steps */
                            jerry_length_t c_arg_cnt) /**< the count of the `c_arg_p` array */
 {
-  jerry_value_t ret = jerry_create_undefined ();
+  jerry_value_t ret = jerry_undefined ();
 
   jerryx_arg_js_iterator_t iterator = { .js_arg_p = js_arg_p, .js_arg_cnt = js_arg_cnt, .js_arg_idx = 0 };
 
-  for (; c_arg_cnt != 0 && !jerry_value_is_error (ret); c_arg_cnt--, c_arg_p++)
+  for (; c_arg_cnt != 0 && !jerry_value_is_exception (ret); c_arg_cnt--, c_arg_p++)
   {
     ret = c_arg_p->func (&iterator, c_arg_p);
   }
@@ -66,18 +66,18 @@ jerryx_arg_transform_this_and_args (const jerry_value_t this_val, /**< the this_
 {
   if (c_arg_cnt == 0)
   {
-    return jerry_create_undefined ();
+    return jerry_undefined ();
   }
 
   jerryx_arg_js_iterator_t iterator = { .js_arg_p = &this_val, .js_arg_cnt = 1, .js_arg_idx = 0 };
 
   jerry_value_t ret = c_arg_p->func (&iterator, c_arg_p);
 
-  if (jerry_value_is_error (ret))
+  if (jerry_value_is_exception (ret))
   {
-    jerry_release_value (ret);
+    jerry_value_free (ret);
 
-    return jerry_create_error (JERRY_ERROR_TYPE, (jerry_char_t *) "'this' validation failed.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, "'this' validation failed.");
   }
 
   return jerryx_arg_transform_args (js_arg_p, js_arg_cnt, c_arg_p + 1, c_arg_cnt - 1);
@@ -99,22 +99,22 @@ jerryx_arg_transform_object_properties (const jerry_value_t obj_val, /**< the JS
 {
   if (!jerry_value_is_object (obj_val))
   {
-    return jerry_create_error (JERRY_ERROR_TYPE, (jerry_char_t *) "Not an object.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, "Not an object.");
   }
 
   JERRY_VLA (jerry_value_t, prop, name_cnt);
 
   for (jerry_length_t i = 0; i < name_cnt; i++, name_p++)
   {
-    const jerry_value_t name_str = jerry_create_string (*name_p);
-    prop[i] = jerry_get_property (obj_val, name_str);
-    jerry_release_value (name_str);
+    const jerry_value_t name_str = jerry_string_sz ((char *) (*name_p));
+    prop[i] = jerry_object_get (obj_val, name_str);
+    jerry_value_free (name_str);
 
-    if (jerry_value_is_error (prop[i]))
+    if (jerry_value_is_exception (prop[i]))
     {
       for (jerry_length_t j = 0; j < i; j++)
       {
-        jerry_release_value (prop[j]);
+        jerry_value_free (prop[j]);
       }
 
       return prop[i];
@@ -125,7 +125,7 @@ jerryx_arg_transform_object_properties (const jerry_value_t obj_val, /**< the JS
 
   for (jerry_length_t i = 0; i < name_cnt; i++)
   {
-    jerry_release_value (prop[i]);
+    jerry_value_free (prop[i]);
   }
 
   return ret;
@@ -144,20 +144,20 @@ jerryx_arg_transform_array (const jerry_value_t array_val, /**< points to the JS
 {
   if (!jerry_value_is_array (array_val))
   {
-    return jerry_create_error (JERRY_ERROR_TYPE, (jerry_char_t *) "Not an array.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, "Not an array.");
   }
 
   JERRY_VLA (jerry_value_t, arr, c_arg_cnt);
 
   for (jerry_length_t i = 0; i < c_arg_cnt; i++)
   {
-    arr[i] = jerry_get_property_by_index (array_val, i);
+    arr[i] = jerry_object_get_index (array_val, i);
 
-    if (jerry_value_is_error (arr[i]))
+    if (jerry_value_is_exception (arr[i]))
     {
       for (jerry_length_t j = 0; j < i; j++)
       {
-        jerry_release_value (arr[j]);
+        jerry_value_free (arr[j]);
       }
 
       return arr[i];
@@ -168,7 +168,7 @@ jerryx_arg_transform_array (const jerry_value_t array_val, /**< points to the JS
 
   for (jerry_length_t i = 0; i < c_arg_cnt; i++)
   {
-    jerry_release_value (arr[i]);
+    jerry_value_free (arr[i]);
   }
 
   return ret;