feat: init migrations for transactional tables (#9946)

# Which Problems Are Solved

To start with transactional tables we need to setup the new `zitadel`
schema in a way that does not rely on the event store later.

# How the Problems Are Solved

Setup step added which calls the function which executes the migrations.

# Additional Changes

none

# Additional Context

- closes #9933

backend/v3/storage/database/dialect/postgres/migration/doc.go

@@ -0,0 +1,13 @@
+// This package contains the migration logic for the PostgreSQL dialect.
+// It uses the [github.com/jackc/tern/v2/migrate] package to handle the migration process.
+//
+// **Developer Note**:
+//
+// Each migration MUST be registered in an init function.
+// Create a go file for each migration with the sequence of the migration as prefix and some descriptive name.
+// The file name MUST be in the format <sequence>_<name>.go.
+// Each migration SHOULD provide an up and down migration.
+// Prefer to write SQL statements instead of funcs if it is reasonable.
+// To keep the folder clean create a folder to store the sql files with the following format: <sequence>_<name>/{up/down}.sql.
+// And use the go embed directive to embed the sql files.
+package migration