Fix GestureRecognizers not filtering `touchesEnded` events properly

[janek]

Type of change: Bug fix

Motivation (current vs expected behavior)

When a user drags around a view with an active UIGestureRecognizer, that recognizer should cancel the touches sent to this view by default (and let them pass if cancelsTouchesInView was explicitly set to false).

This PR improves the handling of UITouch's internal hasBeenCancelledByAGestureRecognizer variable to ensure that happens.

Please check if the PR fulfills these requirements

• [x] Self-review: I am confident this is the simplest and clearest way to achieve the expected behaviour
• [x] There are no dependencies on other PRs or I have linked dependencies through Zenhub
• [x] The commit messages are clean and understandable
• [x] Tests for the changes have been added (for bug fixes / features)

[codecov[bot]]

Codecov Report

Merging #305 into master will not change coverage. The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #305   +/-   ##
=======================================
  Coverage   51.97%   51.97%           
=======================================
  Files          87       87           
  Lines        3161     3161           
=======================================
  Hits         1643     1643           
  Misses       1518     1518

Impacted Files	Coverage Δ
Sources/UITouch.swift	100% <ø> (ø)	:arrow_up:
Sources/UIWindow.swift	71.05% <ø> (-0.75%)	:arrow_down:
Sources/UIGestureRecognizer.swift	88.57% <100%> (+0.33%)	:arrow_up:

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 2bb5fc3...f50e5e8. Read the comment docs.