[Sync::USS] Introduce PasswordSyncStore:ReadAllLogins()

PasswordSyncableService code used two methods in PasswordSyncStore
to retrieve all passwords FillAutofillableLogins() and
FillBlacklistLogins() and then concatenated the results.
This has three issues:
1- This unnecessarily hit the DB twice.
2- Each DB hit involved sorting over some string field that isn't
required.
3-Those calls don't expose the DB primary key of each form which
is required by the new sync architecture.

This CL is replace those APIs in the PasswordSyncStore with a single
API that returns all logins together with the corresponding DB primary
key.

This is in preparation for a later CL that would actually use this API
in the PasswordSyncBridge that belongs to the new sync architecture.

Since the methods FillAutofillableLogins() and FillBlacklistLogins()
are used in the password manager codebase, they have been moved to be
part of the PasswordStore interface rather than the PasswordStoreSync

Bug: 902349
Change-Id: Ic94b83fcc24dfc1833e07653426c064292be5ba7
Reviewed-on: https://chromium-review.googlesource.com/c/1424941
Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Commit-Queue: Mohamed Amir Yosef <mamir@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625225}
13 files changed