[CodeHealth] Makes PwaInstallPathTracker static

It can be static and not owned by AppBannerManager now.

Bug: 327273599
Change-Id: I62f87f450522dbb4466d83f1c651a4a193cd9cd5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5402734


Commit-Queue: Ella Ge <eirage@chromium.org>
Reviewed-by: Glenn Hartmann <hartmanng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1279795}