fix(plugins): restore MySQL zero dates and keep session settings

[datlechin]

Why

TablePro's MySQL dump set only the character set, unlike mysqldump. Under MySQL 8's default SQL mode its zero dates failed with 1292 (#3414), AUTO_INCREMENT 0 was renumbered and TIMESTAMPs shifted between time zones. Imports also left the file's settings on the editor's session.

Change

• MySQL dumps carry mysqldump's SQL_MODE, FOREIGN_KEY_CHECKS and TIME_ZONE lines, are read in UTC under an empty SQL mode, and keep each routine, trigger and event's own SQL mode.
• New PluginKit session scopes (additive, kit 38): imports put back what a file changed on MySQL and PostgreSQL (pg_dump's empty search_path included); MySQL to MySQL Object Copy and Transfer To keep zero dates, AUTO_INCREMENT 0 and TIMESTAMPs.
• PostgreSQL dumps read ISO dates, postgres intervals and full float digits.
• Imports stop claiming a rollback after MySQL committed a DDL; the MySQL driver refreshes its transaction flag after an error.

Verified

scripts/probes/check-mysql-dump-session.sh passes on MariaDB 13.0.2 and MySQL 8.4.11 and fails on the old prologue; check-postgresql-dump-session.sh passes on PostgreSQL 17.11. SQLExportEncodingTests became SQLExportSessionDeclarationTests.

Not in this PR

• Older dumps still need SET SESSION sql_mode = 'NO_AUTO_VALUE_ON_ZERO' before import; no import option, by decision.
• Session restore for other engines; SQL Server DATEFORMAT.
• Docs: docs(features): document dump session settings and import restore docs#21, to merge after this.

Fixes #3414