PointerPoint.Timestamp should be in microseconds

[dr1rrb]

Current behavior

• WPF: ticks ❌ https://github.com/unoplatform/uno/blob/master/src/Uno.UI.Runtime.Skia.Wpf/Input/WpfCorePointerInputSource.cs
• FrameBuffer: microsecconds ✔ https://github.com/unoplatform/uno/blob/master/src/Uno.UI.Runtime.Skia.Linux.FrameBuffer/FrameBufferPointerInputSource.Touch.cs#L37
• GTK: milliseconds ❌ https://github.com/unoplatform/uno/blob/master/src/Uno.UI.Runtime.Skia.Gtk/Input/GtkCorePointerInputSource.cs#L489
• WASM: ticks ❌ https://github.com/unoplatform/uno/blob/master/src/Uno.UI/UI/Xaml/Input/PointerRoutedEventArgs.wasm.cs#L120
• Android: ticks ❌ https://github.com/unoplatform/uno/blob/master/src/Uno.UI/UI/Xaml/Input/PointerRoutedEventArgs.Android.cs#L228C5-L228C5
• iOS: ticks ❌ https://github.com/unoplatform/uno/blob/master/src/Uno.UI/UI/Xaml/Input/PointerRoutedEventArgs.iOS.cs#L106
• X11: ticks ✔️ fix: Fix pointer events timestamp being in ms instead of ticks on X11 #18293
• Injected pointers: ticks ❌ 3da073b#diff-9234e00dd39668a69fae53f8ab09f770f9a1bf557c0d1cf50875197a06cf15f1R106

But some places in uno assume this to be ticks, like the GestureRecognizer for the hold: https://github.com/unoplatform/uno/blob/master/src/Uno.UWP/UI/Input/GestureRecognizer.Gesture.cs#L392. We need to review all usages of this Timestamp property.

The GestureRecognizer.GetVelocities also assume ticks

uno/src/Uno.UI/UI/Input/GestureRecognizer.Manipulation.cs

Line 499 in dc04707

var elapsedTicks = _inertia?.Elapsed ?? (double)_currents.Timestamp - _lastPublishedState.timestamp;

Expected behavior

Micro seconds as on windows The time, relative to the system boot time, in microseconds. (Note: this should be confirmed as it already happen that the docs differs from observations for those kind of core low-level properties).

Anything else we need to know?

This property is documented to be relative to the system boot time, but this might have a negative perf impact on some platforms (e.g. Android) or even completely impossible to get. As this property is usually only used relative to itself (e.g. determine since how long the pointer is down), the only important thing is to have a valid value and in the right unit, the origin is not really relevant.