Move UserCloudPolicyManager and UserCloudPolicyStore into the policy component.

This will enable using those classes on the iOS build.

BUG=271392
TBR=jochen@chromium.org

Review URL: https://codereview.chromium.org/105573005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240359 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240359