refactor(handler): cache active instances (#9008)

# Which Problems Are Solved

Scheduled handlers use `eventstore.InstanceIDs` to get the all active
instances within a given timeframe. This function scrapes through all
events written within that time frame which can cause heavy load on the
database.

# How the Problems Are Solved

A new query cache `activeInstances` is introduced which caches the ids
of all instances queried by id or host within the configured timeframe.

# Additional Changes

- Changed `default.yaml`
  - Removed `HandleActiveInstances` from custom handler configs
- Added `MaxActiveInstances` to define the maximal amount of cached
instance ids
- fixed start-from-init and start-from-setup to start auth and admin
projections twice
- fixed org cache invalidation to use correct index

# Additional Context

- part of #8999

internal/eventstore/handler/v2/mock_test.go

@@ -7,12 +7,17 @@ type projection struct {
 	reducers []AggregateReducer
 }
 
-// Name implements Projection
+// ActiveInstances implements [Projection]
+func (p *projection) ActiveInstances() []string {
+	return nil
+}
+
+// Name implements [Projection]
 func (p *projection) Name() string {
 	return p.name
 }
 
-// Reducers implements Projection
+// Reducers implements [Projection]
 func (p *projection) Reducers() []AggregateReducer {
 	return p.reducers
 }