[backport#15874] Resolve the qt/guiutil <-> qt/optionsmodel CD
Summary:
fa1c8e297 Resolve the qt/guiutil <-> qt/optionsmodal CD (251)
Pull request description:
This pull request attempts to resolve the `qt/guiutil` <-> `qt/optionsmodel` circular dependency. The `Intro` class in `qt/intro` has a static member function `getDefaultDataDirectory` which is used by `qt/optionsmodel` and creates the circular dependency `qt/guiutil -> qt/walletmodel -> qt/optionsmodel -> qt/intro -> qt/guiutil`. This circular dependency is resolved by moving `Intro::getDefaultDataDirectory` to `GUIUtil::getDefaultDataDirectory` without modifying the implementation.
Backport of Core PR15874
Test Plan:
ninja all check check-functional
Reviewers: #bitcoin_abc, PiRK
Reviewed By: #bitcoin_abc, PiRK
Differential Revision: https://reviews.bitcoinabc.org/D8916