Remove PasswordStoreWin class

This CL implements the first step in removing PasswordStoreWin and related code
(more context in the design doc linked at https://crbug.com/456119#c13):
* Deleting the PasswordStoreWin class and replacing it with PasswordStoreDefault
  on Windows.
* Marking a metric measured in the deleted code as obsolete.

Bug: 456119
Change-Id: I326e05101f904e3afd56fbb5dcce22e0ba2f2729
Reviewed-on: https://chromium-review.googlesource.com/1131495
Commit-Queue: Uladzimir Miniailau <miniailau@google.com>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Vaclav Brozek <vabr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576802}
7 files changed