Add tests for ES2015 syntax and run-time features

[ariya]

In addition to prevent any future regressions, this is also useful to demonstrated what is currently being supported.

[vitallium]

Some time ago, while I was preparing a 2.5 binary I used https://kangax.github.io/compat-table/es2016plus/ to test supported features. The old screenshot needs an update.

[stale]

Due to our very limited maintenance capacity, we need to prioritize our development focus on other tasks. Therefore, this issue will be automatically closed (see #15395 for more details). In the future, if we see the need to attend to this issue again, then it will be reopened. Thank you for your contribution!

[stale]

Due to our very limited maintenance capacity, we need to prioritize our development focus on other tasks. Therefore, this issue will be automatically closed (see #15395 for more details). In the future, if we see the need to attend to this issue again, then it will be reopened. Thank you for your contribution!