fix: don't use deprecated ui::MouseEvent constructor (#44868)

* refactor: do not use deprecated gfx::Point constructor for MouseEvent

Deprecated in https://chromium-review.googlesource.com/c/1444251

* refactor: use WebInputEvent::GetTypeAsUiEventType() instead of rolling our own

Added in https://chromium-review.googlesource.com/c/chromium/src/+/2180291