* [Origin] Wait for all policy managers before refreshing profile policies
`BraveProfilePolicyProvider` observes both `BraveOriginPolicyManager`
and `AdBlockOnlyModePolicyManager`. Each fires `OnBravePoliciesReady`
independently, so the first notification could call `RefreshPolicies`
before the other manager's `Init()` had run -- producing a bundle that
reflected only one source and flipping `IsFirstPolicyLoadComplete` true
on the empty load.
Introduce `BravePolicyManagerBase` with self-registration and a static
`AllInitialized()`. `OnBravePoliciesReady` early-returns until every
registered manager reports ready; `policies_ready_` is gated on the
same check so `SetProfileID` can't trigger a partial refresh either.
Future managers inheriting from the base are picked up automatically.
Resolves: https://github.com/brave/brave-browser/issues/55276
Serg
a044cc5bde