Revert of PaymentApp: Introduce PaymentAppDatabase class. (patchset #3 id:100001 of https://codereview.chromium.org/2560293002/ )

Reason for revert:
Broke content_unittests:
[ RUN      ] PaymentAppManagerTest.SetAndGetManifest

[libprotobuf ERROR c:\b\c\b\win\src\third_party\protobuf\src\google\protobuf\message_lite.cc:120] Can't parse message of type "content.PaymentAppManifestProto" because it is missing required fields: (cannot determine missing fields for lite message)

c:\b\c\b\win\src\content\browser\payments\payment_app_manager_unittest.cc(145): error: Value of: payments::mojom::PaymentAppManifestError::NONE

  Actual: PaymentAppManifestError::NONE

Expected: read_error

Which is: PaymentAppManifestError::MANIFEST_STORAGE_OPERATION_FAILED

[  FAILED  ] PaymentAppManagerTest.SetAndGetManifest (3 ms)

Original issue's description:
> PaymentApp: Introduce PaymentAppDatabase class.
>
> The class is providing APIs to read/write payment app related data(e.g. manifest
> and associated service worker). It can be shared between payment_app_manager.cc
> and payment_app_context.cc.
>
> The payment_app_manager.cc contains a actual implementation of the
> PaymentAppManager interface[1] used on the page or worker.
> Also, the payment_app_context.cc can be used to query all manifests data[2]
> in order to update payment request UI in Chrome layer.
>
> We can summarize this CL as follows.
>   1. Rename PaymentAppContext in content/browser/payments to
>      PaymentAppContextImpl and then add PaymentAppContext interface in
>      content/public to expose some APIs to Chrome layer.
>   2. Write PaymentAppDatabase class and then move most of logics to access
>      database from PaymentAppManager to the new class.
>   3. Add a interface to query all manifests data in Chrome layer but it's not
>      implemented yet in this CL. It will be implemented in follow-up CL[2].
>
> [1] https://w3c.github.io/webpayments-payment-apps-api/#payment-app-manager
> [2] https://codereview.chromium.org/2556433002
>
> BUG=661608
> TEST=existing unittests
>
> Review-Url: https://codereview.chromium.org/2560293002

TBR=rouslan@chromium.org,avi@chromium.org,tommyt@opera.com,jinho.bang@samsung.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=661608

Review-Url: https://codereview.chromium.org/2565423002
Cr-Commit-Position: refs/heads/master@{#437861}
14 files changed