Include trailing edge offsets in autoSizeThatFits

[heoblitz]

What is this PR?

Fix autoSizeThatFits so trailing and bottom edge offsets are included in the calculated size.

Closes #276

Reproduction

private func performPinLayout() {
    view1.pin.size(50).start(16).top(16).bottom(16)
    view2.pin.size(50).top(16).end(16).bottom(16)
}

override func layoutSubviews() {
    super.layoutSubviews()
    performPinLayout()
}

override func sizeThatFits(_ size: CGSize) -> CGSize {
    autoSizeThatFits(size, layoutClosure: performPinLayout)
}

sizeThatFits now returns the expected height of 82.

Tests

• LTR and RTL auto sizing, followed by actual frame placement
• Negative leading offsets remain unchanged
• LayoutMethodSpec passes