[FillRecoveryPwd] Pipe backup password to the KA sheet

The backup/recovery password is already correctly stored in the
credentials cache. This CL pipes the information to the Java part of the
Keyboard Accessory sheet where it will be used to offer the credential
for filling.

Since the recovery credential needs to appear immediately after its
corresponding main credential, and since the KA doesn't do its own
credential sorting like Touch-to-Fill does, the sorting logic in
CredentialCache is changed slightly.

Bug:418198645

Change-Id: I3cb6a4d4f6ba1a764ecef5d8970d2201264d82bb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6607184
Commit-Queue: Ioana Pandele <ioanap@chromium.org>
Reviewed-by: Friedrich Hauser <friedrichh@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1468159}