- add a secondary "loading" state (`loadingWithText`), that is show the
loading indicator next to the text
- simplify the StatusBaseButton layout (esp. handling the overall
opacity/visibility)
- add a QML test suite; the code was becoming too complex and adding a
simple boolean prop was getting "dangerous"
- port the SwapModal to use the new `loadingWithText` property
Fixes#15313
Lukáš Tinkl