[Acessibility - Service Workers]: Making status an alert element
[Acessibility - Service Workers]: Making status an alert element

Issue:
- MAS 4.1.3 Status Messages violation
- Sync status is not readily accessible to SR users

Changes:
- Making sync status an alert element so that changes will be announced to the SR

Bug: 1120099
Change-Id: I9814684fcad0c548796896ba2037288c546096c0
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2368055
Reviewed-by: Jose Leal <49360abdd51ad00da751c3d448c2dbea47853f27@microsoft.com>
Commit-Queue: Michael Liao <00d75d81082fdf74688ec453c516b42f7cbf0f40@microsoft.com>

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