[mrkai77]

Previously, a custom swipe or pinch on the same finger count as the radial menu was flagged as a conflict and disabled, so one couldn't, for example, keep a 3-finger radial menu but have a 3-finger swipe up maximize the window. This PR:

1. Lets swipe and magnify gestures take priority over the radial menu's matching direction on the same finger count, instead of conflicting with it. Swipes replace only the slot they land on, so the other directions (including diagonals) still go to the radial menu. Pinching and spreading take over the stroke from the center action once they pass the activation threshold,
2. Only lets an override take over a stroke the radial menu was allowed to start, so titlebar-only gestures still respect their activation zone,
3. Shows a tooltip on gestures that override the radial menu, alongside the existing conflict tooltip,
4. Adds new gestures with no trigger, like how new keybinds have no keys. They show a "Set Gesture…" button, never activate, and never conflict until a gesture is picked,
5. Keeps "No Action" as a deliberate binding, so it still triggers (doing nothing) and still conflicts with a duplicate,
6. Removes custom gesture names, since the trigger already describes the gesture. Existing settings with names still load fine,
7. Removes unnecessary .description calls in log interpolation, and makes GestureBinding and SpaceDestination conform to CustomStringConvertible.

Closes #1177