feat(fields): add instance domain (#9000)

# Which Problems Are Solved

Instance domains are only computed on read side. This can cause missing
domains if calls are executed shortly after a instance domain (or
instance) was added.

# How the Problems Are Solved

The instance domain is added to the fields table which is filled on
command side.

# Additional Changes

- added setup step to compute instance domains
- instance by host uses fields table instead of instance_domains table

# Additional Context

- part of https://github.com/zitadel/zitadel/issues/8999

internal/query/instance_by_domain.sql

@@ -1,6 +1,8 @@
 with domain as (
-	select instance_id from projections.instance_domains
-	where domain = $1
+	SELECT instance_id FROM eventstore.fields
+	WHERE object_type = 'instance_domain'
+	AND object_id = $1
+	AND field_name = 'domain'
 ), instance_features as (
 	select i.*
 	from domain d