fix(tests): Make tabNavigateToWorkspace idempotent

Previously this function would just send a bunch of tabs, which
depended on focus state being as-on-document-load.  Some tests
(notably the ones in basic_test.ts) that have only a suiteSetup
and not a (per-test) setup method were only were only passing
because of the combination of:

* Due to issue #632, pressing tab when the workspace is focused
  (and there are no further focusable elements on the page)
  incorrectly causes focus to move to the first focusable element
  on the page instead of (as would normally be the case) to the
  browser controls, and
* The fact that the index.html had exactly one additional focusable
  div on the page, preceding the injection div.

This meant that calling tabNavigateToWorkspace when the workspace
was already focused would, only by sheer coincidence, result in the
focus remaining on the workspace.

By explicitly focusing a known element, tabNavigateToWorkspace
should work correctly regardless of how many focusable elements
are on the page and which one (if any) was focused before the call.

Author: cpcallen

test/webdriverio/test/test_setup.ts

@@ -455,8 +455,14 @@ export async function tabNavigateToWorkspace(
   hasToolbox = true,
   hasFlyout = true,
 ) {
-  // Navigate past the initial pre-injection focusable div element.
-  await tabNavigateForward(browser);
+  // Move focus to initial pre-injection focusable div element.
+  //
+  // Ideally we'd just rest focus state to the state it is in when the
+  // document initially loads (and then send one tab), but alas
+  // there's no straightforward way to do that; see
+  // https://stackoverflow.com/q/51518855/4969945
+  await browser.execute(() => document.getElementById('focusableDiv')?.focus());
+  // Navigate to workspace.
   if (hasToolbox) await tabNavigateForward(browser);
   if (hasFlyout) await tabNavigateForward(browser);
   await tabNavigateForward(browser); // Tab to the workspace itself.