Editorial improvements to unhandled promise rejections

[domenic]

What is the issue with the HTML Standard?

Since https://html.spec.whatwg.org/#unhandled-promise-rejections was written, a few spec best practices have changed. #10404 significantly improves unhandled exception handling, and we want to align unhandled promise rejections with that.

We should make the following changes:

• Move the outstanding rejected promises weak set and about-to-be-notified rejected promises list to global objects, instead of environment settings objects. The definitions should be in the secion Realms, settings objects, and global objects, as a sibling of the sentence introduced in Create a 'report an exception' algorithm per #958 #10404 that defines "in error reporting mode".

• Change "notify about rejected promises" to operate entirely on global objects.

• Change "notify about rejected promises" to directly report to the developer console, like "report an exception" does after Create a 'report an exception' algorithm per #958 #10404. Delete the "handled" and "not handled" concepts. (But preserve their IDs, by adding id="" attributes to the step inside "report an exception" that reports to the developer console.

• Update "p's [[PromiseIsHandled]] internal slot" to "p.[[PromiseIsHandled]]", and "the value of p's [[PromiseResult]] internal slot" to "p.[[PromiseResult]]".