Implement touch/pen event support in marionette

[jgraham]

Implement support for touch and pen events in marionette. This will improve our ability to write platform tests using wpt, improve author's ability to write tests that work in Firefox, and improve our support for the existing pointerevents testsuite https://wpt.fyi/results/pointerevents?label=master&label=experimental&aligned&q=pointerevents

[karlcow]

To create a JIRA issue for it

[karlcow]

https://mozilla-hub.atlassian.net/browse/FFXP-1626

[jgraham]

In the end it made more sense to scope this to touch and wheel events. I could add pen events — there's no additional complexity that I'm aware of — but I aiui the support in gecko is platform-specific, so it seems less useful.