Add --test262-esnext option to run-tests.py (#4027)

Changes:
- Imported and unified test262 test harness for ES2015 and ESNext
- Simplified runner scripts accordingly
- Run tests on CI to be able detect regressions and progressions too

JerryScript-DCO-1.0-Signed-off-by: Csaba Osztrogonác csaba.osztrogonac@h-lab.eu

tests/test262-es6.patch

@@ -1,24 +0,0 @@
-diff --git a/tools/packaging/test262.py b/tools/packaging/test262.py
-index 921360a05e..a19c8a14e6 100755
---- a/tools/packaging/test262.py
-+++ b/tools/packaging/test262.py
-@@ -168,6 +168,8 @@ class TestResult(object):
-     if len(err) > 0:
-        target.write("--- errors ---  \n %s" % err)
- 
-+    target.write("\n--- exit code: %d ---\n" % self.exit_code)
-+
-   # This is a way to make the output from the "whitespace" tests into valid XML
-   def SafeFormat(self, msg):
-     try:
-@@ -469,8 +471,8 @@ class TestSuite(object):
-           if self.ShouldRun(rel_path, tests):
-             basename = path.basename(full_path)[:-3]
-             name = rel_path.split(path.sep)[:-1] + [basename]
--            if EXCLUDE_LIST.count(basename) >= 1:
--              print 'Excluded: ' + basename
-+            if rel_path in EXCLUDE_LIST:
-+              print 'Excluded: ' + rel_path
-             else:
-               if not self.non_strict_only:
-                 strict_case = TestCase(self, name, full_path, True)