[FedCM] Fix num_fetches_for_idp_signin

The FetchData is reset in MaybeShowAccountsDialog() so we move the
member to outside of this structure so that it is not reset there.
Instead, we only need to reset it in CleanUp. And we keep a boolean
for each IDP so that we can decide to only show filtered out accounts
for IDPs for which the user has already tried to login to at least
once.

Bug: 40945672
Change-Id: I5bd999a146c1aa983dace43f15f20cf3cbdbfe68
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5979728
Commit-Queue: Nicolás Peña <npm@chromium.org>
Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1376059}