* Don't purge cards-by-rarity cache between tournaments
* Move DOM and WAR specific checks out of base ExpansionSet class
* Move Battlebond specific methods out of base ExpansionSet class
* Refactor ExpansionSet and subclasses
* Zendikar boosters also only have full-art basic lands
* Fix Eldritch Moon (#8171)
- replacing hard coded strings of set codes with reference to 'mage.sets.<set>.getInstance().getCode()' allows for set class names to no longer show as unreferenced & adds for more consistence between other block units
- various protected variables were able to be changed to private to clean up additional warnings
- some JavaDoc comments were generating warnings due to missing documentation
- removed some unused imports and unused variables
- there were multiple conditional logic checks for 'rarity != Rarity.LAND' within an if block where the outer condition was 'if rarity == Rarity.COMMON' rendering the inner condition always true and thus redundant
- a few ExpansionSet.buildDate parameters wer using octal values (eg. '03' instead of '3') which triggered some warnings
- added a booster generation test for WarOfTheSparks to make sure every booster contains a planeswalker
- added a booster generation test for ModernHorizons to make sure every booster contains a snow land
- booster generation test for Battlbond set referenced the Coldsnap set class instead of Battlebond
