Bugfix/fit to bounds constrains

[GrigoryUlanov]

Fix for this issue #294

Constraints break when we set fitToBounds contentMode and surfaceView.contentInsets.

The main problem was in heightConstraint between contentView and FloatingPanelSurfaceView taking into account surfaceView.contentInsets and offConstraints from FloatingPanelLayoutAdapter which do not take into account surfaceView.contentInsets.

Constrains error example:

[LayoutConstraints] Unable to simultaneously satisfy constraints.
	Probably at least one of the constraints in the following list is one you don't want. 
	Try this: 
		(1) look at each constraint and try to figure out which you don't expect; 
		(2) find the code that added the unwanted constraint or constraints and fix it. 
(
    "<NSLayoutConstraint:0x600002010460 FloatingPanel.FloatingPanelSurfaceView:0x7feb4f46d170.bottom == FloatingPanel.FloatingPanelPassThroughView:0x7feb4f7736f0.bottom   (active)>",
    "<NSLayoutConstraint:0x6000020105a0 V:[FloatingPanel.FloatingPanelPassThroughView:0x7feb4f7736f0]-(0)-[FloatingPanel.FloatingPanelSurfaceView:0x7feb4f46d170]   (active)>",
    "<NSLayoutConstraint:0x600002010820 UIView:0x7feb4f472ec0.height == FloatingPanel.FloatingPanelSurfaceView:0x7feb4f46d170.height - 35   (active)>"
)

[scenee]

@GrigoryUlanov Thank you so much for your PR!! I will confirm this issue and this fix just to be sure 👍

[scenee]

This makes sense. I also confirmed it's working well for the intrinsic layout. I really appreciate it.