[Platform:Dashboards:DashboardViewMode] Dashboard in full screen mode is not announced.

[bhavyarm]

Description
When user clicks on full screen mode, the dashboard being viewable in full screen mode is not announced. Instead voiceover just reads out the dashboard name.

Preconditions
Dashboards->Dashboard->Full screen button

Steps to reproduce

1. Navigate to Dashboards
2. Click a single dashboard open
3. Run voiceover
4. Click full screen button
5. Dashboard opens in full screen
6. Voiceover doesn't announce that dashboard is in full screen
7. Same when user presses escape to get out of full screen

Kibana Version: 8.18.0

OS: OS X

Browser: Chrome latest

WCAG or Vendor Guidance (optional)

• Understanding SC 4.1.2: Name, Role, Value (Level A)(https://www.w3.org/WAI/WCAG22/Understanding/name-role-value.html)

Related to: https://github.com/elastic/kibana-team/issues/1559

[elasticmachine]

Pinging @elastic/kibana-accessibility (Project:Accessibility)

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)