Release v2.7.2

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This release backports the bug fixes implemented in newer DBAL versions.

Total issues resolved: **7**

**Platforms:**

- [3103: Added keywords OVER and RETURNING for MariaDb102](https://github.com/doctrine/dbal/pull/3103) thanks to @mdriessen

**Schema Comparison:**

- [3086: Postgres, Oracle and SQL Server Sequence increment_by & min_value as int](https://github.com/doctrine/dbal/pull/3086) thanks to @simPod
- [3210: Unnecessary alter sequence queries generated on Oracle db during schema update](https://github.com/doctrine/dbal/issues/3210) thanks to @bobvandevijver

**Performance:**

- [3114: Portability Statement still fetches all data in iterator mode](https://github.com/doctrine/dbal/issues/3114) thanks to @morozov
- [3115: Replaced ArrayIterator with StatementIterator in Portability\Connection](https://github.com/doctrine/dbal/pull/3115) thanks to @morozov

**Documentation**:

- [3121: Document how to opt-in for deprecations](https://github.com/doctrine/dbal/issues/3121) thanks to @Majkl578
- [3123: Opt in deprecations docs](https://github.com/doctrine/dbal/pull/3123) thanks to @greg0ire