[WebLayer] Move disconnectForStrictShow, mRejectShowErrorMessage

Moved disconnectForStrictShow, mRejectShowErrorMessage from CPRService
to PRService, because they are the logic that is shareable with
WebLayer.

Change: 1144527

Change-Id: I1449b7e145918f057e7289984a4eb7364f05e900
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2519202


Commit-Queue: Liquan (Max) Gu <maxlg@chromium.org>
Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#824631}