[Sync] Notify observers when data types stopped due to preconditions

Prior to this CL, OnSingleDataTypeWillStop() ignored any failures which
are already in DataTypeStatusTable, which was supposed to detect new
failures only. But DataTypePreconditionChanged() updates the table first
and only then stops the data type (which will eventually call
OnSingleDataTypeWillStop), so in practice it's a new failure which is
ignored, hence no reconfiguration is happening and observers are not
notified about the changes.

This CL also fixes data type precondition update code path because it
could start DataTypeManager configuration before the sync engine is
initialized (and hence violate some DCHECKs). Now any precondition
changes are ignored if data type manager is stopped.

Clearing metadata for stopped types is also moved to ModelLoadManager
similar to disabled types.

Bug: 1491071
Change-Id: Ib43c87464f51dee2d1c825abfc79248d4b3d2796
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4931489
Reviewed-by: Ankush Singh <ankushkush@google.com>
Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Rushan Suleymanov <rushans@google.com>
Cr-Commit-Position: refs/heads/main@{#1209352}