Add MariaDB with DuckDB storage engine

[mariadb-AlekseiBukhalov]

MariaDB storage plugin embedding DuckDB v1.5.2 (ha_duckdb). Queries run via standard MariaDB SQL interface; DuckDB handles execution.

Machine: c6a.4xlarge · Date: 2026-06-19

Metric	MariaDB+DuckDB	DuckDB
Sequential hot total	25.3 s	26.3 s
Concurrent QPS	1.198	0.705
Concurrent error ratio	0.000	0.998
Load time	375.8 s	126 s

Source: https://github.com/drrtuy/mdb-server (branch bb-11.4-duckdb-jemalloc)

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}