feat(db): adding relational instance table (#10007)

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# Which Problems Are Solved

Implementing Instance table to new relational database schema

# How the Problems Are Solved


The following fields must be managed in this table:

- `id`
- `name`
- `default_org_id`
- `zitadel_project_id`
- `console_client_id`
- `console_app_id`
- `default_language`
- `created_at`
- `updated_at`
- `deleted_at`

The repository must provide the following functions:

Manipulations:
- create
  - `name`
  - `default_org_id`
  - `zitadel_project_id`
  - `console_client_id`
  - `console_app_id`
  - `default_language`
- update
  - `name`
  - `default_language`
- delete

Queries:
- get returns single instance matching the criteria and pagination,
should return error if multiple instances were found
- list returns list of instances matching the criteria, pagination

Criteria are the following:
- by id

pagination:
- by created_at
- by updated_at
- by name

### instance events

The following events must be applied on the table using a projection
(`internal/query/projection`)

- `instance.added` results in create
- `instance.changed` changes the `name` field
- `instance.removed` sets the the `deleted_at` field
- `instance.default.org.set` sets the `default_org_id` field
- `instance.iam.project.set` sets the `zitadel_project_id` field
- `instance.iam.console.set` sets the `console_client_id` and
`console_app_id` fields
- `instance.default.language.set` sets the `default_language` field
- if answer is yes to discussion: `instance.domain.primary.set` sets the
`primary_domain` field

### acceptance criteria

- [x] migration is implemented and gets executed
- [x] domain interfaces are implemented and documented for service layer
- [x] repository is implemented and implements domain interface
- [x] testing
  - [x] the repository methods
  - [x] events get reduced correctly
  - [x] unique constraints

# Additional Context

- Closes https://github.com/zitadel/zitadel/issues/9935

backend/v3/storage/database/database.go

@@ -14,6 +14,12 @@ type Pool interface {
 	Close(ctx context.Context) error
 }
 
+type PoolTest interface {
+	Pool
+	// MigrateTest is the same as [Migrator] but executes the migrations multiple times instead of only once.
+	MigrateTest(ctx context.Context) error
+}
+
 // Client is a single database connection which can be released back to the pool.
 type Client interface {
 	Beginner
@@ -30,8 +36,9 @@ type Querier interface {
 }
 
 // Executor is a database client that can execute statements.
+// It returns the number of rows affected or an error
 type Executor interface {
-	Exec(ctx context.Context, stmt string, args ...any) error
+	Exec(ctx context.Context, stmt string, args ...any) (int64, error)
 }
 
 // QueryExecutor is a database client that can execute queries and statements.