Enable the full phpBB test matrix and fix the strict-mode fixture

[bonelifer]

Summary

• Enables the standard phpBB test framework's MySQL/MariaDB, PostgreSQL, and Windows IIS jobs. SQLite and MSSQL coverage stays enabled, and functional tests run throughout the matrix.
• Fixes the restriction-expiry test fixture for MySQL strict mode. The group rows omitted group_desc, which has no default on MySQL/MariaDB. Supplying an empty description lets the fixture load and the existing assertions run.

Test plan

• The first expanded run reproduced the fixture error on MariaDB 10.1: Field 'group_desc' doesn't have a default value.
• After the fixture fix, all 31 jobs passed in the full framework run, including MySQL/MariaDB, MyISAM, PostgreSQL, SQLite, MSSQL, and Windows IIS. MySQL 5.7 and PostgreSQL 14 run across PHP 7.4 and 8.0-8.4.
• Fixture XML parsing, row/column counts, and git diff --check passed locally.
• This PR reruns the standard framework and PHP lint workflows against the final changes.

cc @kaileymsnay

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Investigated and written by Codex on behalf of William Jacoby (bonelifer).