This PR reworks the way Qt dependency is built :-
- Introduces a top level config/build which
- Simplifies the way Qt is built, removing confusing lines
- Resolves static build for #16883
- Mimic how Qt is built from repo/all-in-one
- Is related to bitcoin#20504 which makes (q)make commands simpler
- Continuation/Completion of https://github.com/icota/bitcoin/commit/683710e072eb90296ae5a57f53bce7cac799fc41 which had incomplete dependency chain.
While trying to add Qml/QtQuick i took a closer look at how QT builds and found that it uses a top level qt.pro which by far simplifies the build process.