Effects: read effect data for decks added after initial setup

[ronso0]

Closes #12277

EffectsManager::readEffectsXml is responsible for initialising/restoring Quick Effects, though it only cares about existing decks when it's called (once) via CoreServices::initialize -> EffectsManager::setup. The deck count is still the initial 2 then, the default count PlayerManager is initialized with.
If any decks are added later on, e.g. when the default (4-deck) skin LateNight is loaded, effects.xml is not read again and the Quick Effect slots remain empty.
On next start it uses the deck_count attribute from soundconfig.xml.

IMO only EffectsManager should be responsible for effect defaults, not the Preferences.

Fixed by creating a separate, stripped down version of readEffectsXml that extracts only the Quick Effect for one deck, and call that each time a deck is added after the initial setup() call.

[daschuer]

Normally we prefer initialization with = QDir settingsPath = m_pConfig->getSettingsPath();
To have a clear visible distinguishing from a function call.

Recently we have discussed to prefer initialization lists like:
QDir settingsPath{m_pConfig->getSettingsPath()};

This is just a hint, because that never made the way into our style guides.

[ronso0]

ackknowldeged.
It's copy/paste from readEffectsXml(), and actually it's mixed in the vaious effect managers already:
QString xyPath(m_pConfig->getSettingsPath() + ...);
QDir xyDir(xyPath);
vs
QFile xyFile(m_pConfig->getSettingsPath() + ...);

[daschuer]

LGTM, just code style hints.

[daschuer]

This can become a range based loop, to get rid of i.

[ronso0]

There's QList::iterator, but none for QDomeNodeList.

[daschuer]

Ok than let's merge. Thank you. LGTM.