Implement a RTL support for client side "helper" widgets

Originally by @johannest

Implement a RTL support for the client-side "helper" widgets. At least widgets below have to supported. Assumed changes/tasks are listed below of each widgets.

VTooltip & TooltipInfo
- get direction from owner (if it is HasDirection) by implementing setOwner
- description element css
- testing (manual and TB tests)
VErrorMessage
- get direction when setOwner is called
- RTL css
- testing (manual and TB tests)
VCaption
- get direction from owning component
- mirrored Icon placement
- css for captionText
- css for errorIndicatorElement and requiredFieldIndicator
- testing (manual and TB tests)
com.vaadin.client.ui.FontIcon and ImageIcon
- css
- testing (manual and TB tests)
VOverlay
- ???
VLoadingIndicator
- mirrored
- testing (manual and TB tests)
VContextMenu
- get direction from actionOwner??
- CMenuBar
- show menu on the left side of the cursor
- open nested menus on the left side (can there be nested context menus??)
- css for menu item
- icons on the right side
- testing (manual and TB tests)
vaadin.client.ui.Action
- get direction from actionOwner??
- icon and caption reversed + css for caption
- testing (manual and TB tests)
VUI / UIConnector
- direction for loading indicator
- direction for notifications

Imported from https://dev.vaadin.com/ issue #16545

Start by inspecting the named client-side entry points: VTooltip, VErrorMessage, VCaption, FontIcon, ImageIcon, VOverlay, VLoadingIndicator, VContextMenu, Action, VUI, and UIConnector. Review existing manual and TB tests, then map the listed direction, mirroring, CSS, menu, and notification requirements to those classes. Done means the listed widgets support RTL consistently and the manual and TB tests cover the behavior; VOverlay and action-owner direction still need clarification.