Workspace toolbar item fails WCAG Use-of-color at narrow breakpoint

Follow-up to #2949991-31: Add workspace UI in top dialog. Originally fixed in #33 there, but regression happened before the final commit.

Problem/Motivation

There's a WCAG level A issue at narrow breakpoints, for SC 1.4.1 Use of Color.

At narrow breakpoints, the text labels are not visible for toolbar buttons. So a user can only tell the difference between the live and stage workspaces by colour alone. The icon is the same in each case, and the distinguishing text has been removed. Colour is the only distinguishing feature.

Live workpace active. Green is the only clue:

Stage workspace active. Yellow is the only clue:

Some users may have considerable difficulty knowing which workspace they are viewing. This impacts scenarios like:

• People with colour blindness
• People using tools which adjust the colour-space of their device (Windows/Edge high-contrast theme, iOS white-point adjustment, evening blue-light reduction, ...)
• People using their device in sunlight (e.g. reviewing changes with a phone, sitting next to the window on a train journey, on a sunny day, just before a client meeting...)

This should be addressed before marking the Workspace module as stable. As a level-A WCAG issue, I'd say it's a stable blocker.

Proposed resolution

Instead of removing text labels from all toolbar buttons, we keep the text label for the workspace. Now it's possible to tell the workspaces apart without relying on colour vision:

There's a risk the workspace name could be too long, but we could truncate it if it would be more than, say half the viewport width.

The intended styles are from .toolbar .toolbar-icon-workspace, at line 189 in core/modules/workspace/css/workspace.toolbar.css.
However these are being overridden by more specific rules from .toolbar .toolbar-bar .toolbar-tab > .toolbar-icon, in toolbar.icons.theme.css

Remaining tasks

Review

User interface changes

Show the name of the workspace in the toolbar at narrow breakpoints. Principally to help people with colour blindness. Long workspace names will be truncated.

API changes

None.

Data model changes

None.