Pinch to zoom: change TextView fontSize

[mzorz]

When zooming into a sticker or text, it's often the case it gets pixelated. We should not only change the visual rendering but also change the fontSize on the fly as the user pinches in/out, to avoid losing quality.

[mzorz]

To tackle this one, see technique used in #199

[mzorz]

After intense search for a way that would work, a few things made us reach a conclusion that this issue should be closed with won't fix.

The sequence of PRs #204, #208, #209, #210, #211 and #214 (plus satellite PRs such as #206 and #213) are the trunk of this new solution involving the refactor of touch handlers, in an attempt to get the best of both worlds (view scaling and fontSize adjusting).

However, the impact and energy invested didn't prove to get us much gain, and introduces other problems. These are all described in the last PR #214 (comment).

For these reasons, closing this issue as we've decided to move on with other aspects of the app.