consolidate information about qttranslations catalogs

qttranslations defines catalogs that collect the translations of a set of modules.

Example:

add_ts_targets(qtdeclarative DIRECTORIES qtdeclarative/src
               EXCLUDE declarative/src/quickcontrols2/designer)

windeployqt hardcodes the mapping "module -> catalog" like this:

static QtModuleEntry qtModuleEntries[] = {
...
    { QtQmlModule, "qml", "Qt6Qml", "qtdeclarative" },
    { QtQuickModule, "quick", "Qt6Quick", "qtdeclarative" },
...
}

Other deployment methods also require such a mapping - unless they just deploy all translations.

The mapping in windeployqt is already not quite up-to-date. We should not have these hard-coded mappings. There should be some way to have qttranslations as authoritative source for the module -> catalog mapping.

Ideally, the table at https://doc.qt.io/qt-6/internationalization.html#available-catalogs would also be automatically updated based on the information in qttranslations.