Configure default state of Allow extensions from other stores setting

This policy allows you to control the default state of the Allow extensions from other stores setting.
This policy can't be used to stop installation of extensions from other stores such as Chrome Web Store.
To stop installation of extensions from other stores, use the Extension Settings policy: https://go.microsoft.com/fwlink/?linkid=2187098.

When enabled, Allow extensions from other stores are turned on. So, users don't have to turn on the flag manually
while installing extensions from other supported stores such as Chrome Web Store. However a user can override this setting.
If the user turned on the setting and then turned it off, this setting may not work.
If the Admin first sets the policy as Enabled, but then changes it to not configured or disabled, it has no impact on
user settings and the setting remains as it is.

When disabled or not configured, the user can manage the Allow extensions from other store setting.