This CL adds a `force_unregister_os_integration` entry to the
WebAppSettings policy that allows admins to remove all OS
integration silently for a web app without uninstalling them
fully. This is being done as a mitigation measure for
crbug.com/1476987.

This is a cherry-pick of crrev.com/c/4867130 for M118. This is not
a clean cherry-pick because the lines in https://source.chromium.org/chromium/chromium/src/+/main:chrome/browser/web_applications/policy/web_app_policy_manager.cc;l=109-117?q=WebAppPolicyManager needed to be removed since they are not available in M118.

(cherry picked from commit 2c7a7611d599c705ecc7f709c0b4b44b5b033c3c)

Bug: 1482803, b/300429265
Change-Id: Ib27e3872b8213036d70bd1fb0938c82a5527b758
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4867130
Commit-Queue: Dibyajyoti Pal <dibyapal@chromium.org>
Reviewed-by: Igor <igorcov@chromium.org>
Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1197166}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4874560
Reviewed-by: Alvin Ji <alvinji@chromium.org>
Cr-Commit-Position: refs/branch-heads/5993@{#659}
Cr-Branched-From: 511350718e646be62331ae9d7213d10ec320d514-refs/heads/main@{#1192594}