Fix clickhouse schema dump with non-default database

[Flamefork]

This fixes the issue of using a generated schema.sql with ClickHouse in Docker.
The ClickHouse entrypoint runs every .sql file in /docker-entrypoint-initdb.d during server startup, but it executes them against the default database.

It works if the schema dump was created from the default database, but it fails otherwise:

/entrypoint.sh: running /docker-entrypoint-initdb.d/schema.sql
Received exception from server (version 25.3.6):
Code: 60. DB::Exception: Received from 127.0.0.1:9000. DB::Exception: Table default.schema_migrations does not exist. Maybe you meant my_database_name.schema_migrations?. (UNKNOWN_TABLE)

This fix prefixes migrations_table_name with db_name. in the generated schema, making it consistent with the table creation statements and with other drivers.

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Note

Ensures ClickHouse schema dumps are fully qualified with the database name and consistently quoted.

• Use quotedDatabaseName() in CreateDatabase and schema generation; add helper for quoting the current database
• Change schemaDump to derive the database name internally (remove param)
• Prefix migrations INSERT with db.table in schemaMigrationsDump
• Update tests to expect qualified table names and revised schema output

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