[PWA] Migration for removal of WebAppRegistrar::IsInstalled

This refactors all calls to WebAppRegistrar::IsInstalled to instead
use the new & supported method IsInstallState. This is a purely
non-functional change.

This change is for directory:
chrome/browser/ui/ash/system_web_apps

This CL was uploaded by git cl split.

R=jimmyxgong@chromium.org

Bug: 340952100
Change-Id: I79772cb0d7dffcc2ca2805ad4f2c65ab289ae8a7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6020559
Reviewed-by: Chad Duffin <chadduffin@chromium.org>
Auto-Submit: May Siem <msiem@chromium.org>
Reviewed-by: Jimmy Gong <jimmyxgong@chromium.org>
Commit-Queue: Chad Duffin <chadduffin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1383775}