Reuse the Switch component for the debugger

[jtpio]

When the debugger was added to core there was no default switch component in lab yet: #8010

So it brought its own here:

jupyterlab/packages/debugger/style/icons.css

Line 11 in 5c4e5bf

.jp-Toolbar-item .jp-ToggleSwitch {

Now that ui-components has a Switch, currently used to toggle the single document mode:

We should be able to reuse in the debugger extension too:

jupyterlab/packages/ui-components/src/components/switch.ts

Line 11 in 5c4e5bf

export class Switch extends Widget {

[jasongrout]

Adding to 3.0, not as a blocker, but as (I think) an important ux polish issue for 3.0 if we can get to it.