[Development] New SQL driver: QFIREBIRD build on firebird's OO API

[Andreas Bacher]

Hi,

I'd like to contribute a new SQL driver plugin for the Qt project:
QFIREBIRD, a driver for the Firebird database built on Firebird's modern object-oriented
C++ API (firebird/Interface.h, Firebird 4.0 and later).
QFIREBIRD is meant to coexist with, not replace, the existing QIBASE driver. QIBASE talks
to InterBase/Firebird through the legacy InterBase C API (ibase.h). QFIREBIRD targets
Firebird's current OO API and is offered as an additional option for users on Firebird 4.0+.

Why a new driver rather than extending QIBASE? Several capabilities aren't reachable
through the legacy ibase.h API, e.g.:
- Native batch execution
- Server-side scrollable cursors
- New datatypes (DECFLOAT(16/34), INT128)
- Structured status/error handling (IStatus/FbException)
- Cleaner time zone handling with the OO API

More broadly, the OO API is Firebird's actively developed interface, where new features
land going forward.

Autotests are included: the existing SQL test suite plus QFIREBIRD-specific cases.

Changes are up for review:
Driver: https://codereview.qt-project.org/c/qt/qtbase/+/749083
Docs: https://codereview.qt-project.org/c/qt/qtbase/+/749084
QTBUG-147581: https://qt-project.atlassian.net/browse/QTBUG-147581


BR,
Andreas