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* Move DlpRulesManagerFactory to separate file.
* Separate DlpRulesManager interface and implementation.
* Add missed method to MockDlpRulesManager.
* Remove DlpRulesManagerFactory::OverrideManagerForTesting() and replace
it with direct dependency DataTransferDlpController from
DlpRulesManager.
* Move policy constants to separate file.

TBR=achuith@chromium.org,gab@chromium.org

Bug: 1153146
Change-Id: Ic498947d9bcb41908c9433117a065e19d7afcbcf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2581930
Commit-Queue: Nikita Podguzov <nikitapodguzov@chromium.org>
Reviewed-by: Aya Elsayed <ayaelattar@chromium.org>
Reviewed-by: Sergey Poromov <poromov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836589}