Separate data model errors from syntax errors (unicode-org#708)

* Separate data model errors from syntax errors

Split out data model errors into their own file and
label tests according to the error name from the spec.

No new test cases are added/removed.

* Reformat data model error test file

* Update test/syntax-errors.json

Co-authored-by: Eemeli Aro <eemeli@gmail.com>

* Update test/README.md

Co-authored-by: Eemeli Aro <eemeli@gmail.com>

---------

Co-authored-by: Addison Phillips <addisonI18N@gmail.com>
Co-authored-by: Eemeli Aro <eemeli@gmail.com>

Author: 3 people

test/test-functions.json

@@ -4,7 +4,7 @@
     {
       "src": "{horse :date}",
       "exp": "{|horse|}",
-      "errors": [{ "name": "RangeError" }]
+      "errors": [{ "name": "bad-input" }]
     },
     { "src": "{|2006-01-02| :date}", "exp": "1/2/06" },
     { "src": "{|2006-01-02T15:04:06| :date}", "exp": "1/2/06" },
@@ -23,7 +23,7 @@
     {
       "src": "{horse :time}",
       "exp": "{|horse|}",
-      "errors": [{ "name": "RangeError" }]
+      "errors": [{ "name": "bad-input" }]
     },
     { "src": "{|2006-01-02T15:04:06| :time}", "exp": "3:04 PM" },
     {