Accessibility enhancements in app instal

[AmelBawa-msft]

Summary of the pull request

• Display add/undo button background
  
• Narrator should announce the review tab name
• Narrator should announce the add/undo button state
• Narrator should announce the package name in search mode

References and relevant issues

• https://task.ms/46437516 ([+] button backplate)
• https://task.ms/46729399 (Review page tab name | narrator)
• https://task.ms/46729196 (Add/undo button in search mode | narrator)
• https://task.ms/46729280 (Package name in search mode | narrator)

Detailed description of the pull request / Additional comments

Validation steps performed

PR checklist

• Closes #xxx
• Tests added/passed
• Documentation updated