Meta-issue: update WPT to cover Pointer Events Level 3

[patrickhlauke]

Meta-issue to keep track of any changes to existing tests, and additions/new tests, for PE3 https://wpt.fyi/results/pointerevents / https://github.com/web-platform-tests/wpt/tree/master/pointerevents

We should go through https://w3c.github.io/pointerevents/#revision-history and make sure that we have full test coverage, where possible.

UPDATE: gone through all PRs from the revision history https://w3c.github.io/pointerevents/#revision-history and marked them with "wpt" label https://github.com/w3c/pointerevents/issues?q=is%3Aclosed+label%3Awpt+ (unless they looked purely editorial). This also includes a few non-normative notes and such.

As suggested in the call today, if you could have a look through these issues, remove the label where it's not actually appropriate (doesn't need a test because it's purely informative, is not something that can actually be tested, or where a test already exists) - and if so, leave a comment on the relevant PR explaining why you removed the label. At the end, we should be left just with the PRs that do require new web platform tests, which we can then split out.

[patrickhlauke]

All PRs that need WPT have now been marked as https://github.com/w3c/pointerevents/issues?q=label%3Aneeds-wpt+