Tree: on focus announce up / down arrows are used for navigation

[AccessibilityTestingTeam-TCS]

Environment Details:
VSCode Version : 1.24.1
OS Version : Win10

Additional Details:
ScreenReader Version: NVDA2018.2

Repro Steps:

1. Launch VS Code while NVDA is ON.
2. Go to View menu and Select Extensions
3. Type something in the Search textbox, and press tab key

Actual:
NVDA does not read instructions for navigating inside the treeview.

Expected:
When the focus is on treeview, NVDA should read use up/down arrow keys to navigate inside the treeview.

Recommendations:
Refer below link which is repository of bug fixes code snippets:
https://microsoft.sharepoint.com/teams/msenable/mas/pages/browse-fixes.aspx

User Impact:
User might face problem in navigating inside the treeview if screenreader would announce the instructions.

Attachment for Reference:
A11y VSCode Usability Extensions missing instructions.pptx

Does this issue occur when all extensions are disabled?: Yes

[vscodebot]

(Experimental duplicate detection)
Thanks for submitting this issue. Please also check if it is already covered by an existing one, like:

• [Accessibility]A11y_VSCode_ViewExplorer_ScreenReader: Screenreader does not read the necessary information to navigate within the treeview section. (#52009)
• [Accessibility[Usability]]A11y_VSCode_ViewExplorer_ScreenReader: Screenreader does not read the state as "collapsed" when action is performed on the control. (#52601)
• [Accessibility][Usability]A11y_VSCode_DebugConsole_ScreenReader: NVDA does not read the results at the time when user runs the command. (#52404)
• [Accessibility][Usability]A11y_VSCode_ViewExtensions_ScreenReader: NVDA does not announce any information about the data changing dynamically in treeview. (#52611)
• [Accessibility]A11y_VSCode_ViewExplorer_ScreenReader: Missing grouping for treeview items within "Open Editors" and "File Explorer" section. (#52008)

[isidorn]

Disagree. We use the same navigation in all our trees across the workbench.
Though assigning to @joaomoreno to consider announcing that up/down are used for navigation whenever tree gets focus. IMHO this is superflous

[isidorn]

@joaomoreno I see you have tackled this only for the extensions view? Should we do it for all other views as well?

[joaomoreno]

Pushed one more commit.