Add keyboard modifiers to entity pointer events

[HifiExperiments]

https://github.com/overte-org/overte/issues/808

idk why we never did this 🤷

The values aren't super intuitive (https://doc.qt.io/qt-6/qt.html#KeyboardModifier-enum) e.g. shift = 0x02000000 = 33554432. I'm not sure if the raw enum is exposed automatically since it's Qt? do people think this is sufficient?

[SilverfishVR]

A bit late, but works on Master Overte-308-a1089b5