Schema fixtures: strategy detection, typed inserts and cleanup bugs; missing features #102

Review findings for the Schema fixtures, split into one issue per topic. The details, file:line references and verification status are in the sub-issues.

Milestone 7.x (no breaking changes)

• Schema: strategy detection (DAMA, :memory:, drivers) and password in exception #121
• Schema: foreign keys and transactions when inserting fixtures #123
• Schema: cleanup between tests leaks rows or ids #124
• Schema: schema caching and rebuilding across tests #125
• Schema: prepare for DBAL 5 and fix the README #127
• Schema: PostgreSQL, paratest support and DataBuilder helpers #128

Milestone 8.0 (breaking changes)

• Schema: insert fixture rows with column types #122
• Schema: MySQL cleanup should only touch tables from the SchemaBuilder #126

Removal of deprecated APIs and UPGRADE-8.0.md: #137