Rename timer_update → timer, add AdaptEventCx, pass only ConfigCx to Widget::_nav_next

[dhardy]

This is a series of fixes and tweaks used while updating 7GUIs.

• Remove parameter first of EventState::request_timer_update since it is reasonable to always use true
• Rename timer_update → timer for brevity
• Add AdaptConfigCx and AdaptEventCx. These are essentially ConfigCx / EventCx plus an Id, allowing some methods to be called without specifying an id (for use from methods like Adapt::on_configure). This is very much a half-baked addition; likely more methods should be supported, possibly these should be moved to kas-core, possibly even integrated with ConfigCx and EventCx (the latter is not ideal since various methods such as _send impls would need to update the id both before and after recursing to children).
• Remove MatrixData::ColKey: DataKey and RowKey: DataKey bound (not needed)
• Pass only ConfigCx (instead of EventCx) into Widget::_nav_next. This fixes a slightly obscure bug where ListView::_nav_next would set EventCx::scroll, nothing would handle or clear this, and later a debug_assert! on EventCx::send_event would fail.
• Fix infinite loop in ListView::_nav_next and MatrixView::_nav_next
• Fix handling of (Lost)KeyFocus with mouse input