Merge changes from origin/7.1

ffb33be Update slider client-side state object on value change (#12676)
b8828e7 Only publish files actually produced by this test/browser
5966f01 reduce reflow and calculation in VOverlay (#12566)
600f5f3 Do not try to focus invisible components which not present in UIDL #12654
d0e604f Only print testbench failure TeamCity messages when running in TC
0e9ff32 Ported regression fixes in 6.8 for #12407 to 7.1 branch
267a4ca Fix OptionGroup elements losing focus on value change (#10451)
07ca622 Fixes #12564 (HorizontalLayout breaks w/ alignment & error indicator)

Change-Id: I73bd688d390bcec9ea3c92a2ede4cad3c9daf7dc

diff --cc client/src/com/vaadin/client/ui/VOverlay.java
Simple merge

diff --cc client/src/com/vaadin/client/ui/VScrollTable.java
Simple merge

diff --cc client/src/com/vaadin/client/ui/ui/UIConnector.java
Simple merge