[DeckList] Add custom deck zones to the deck tree

Introduce user-definable zones nested under a board zone (main, side
or maybeboard) so players can organize cards inside a board without
changing board semantics.

- addCustomZone, renameCustomZone, moveCustomZone and removeCustomZone
  manage zones. Names are unique across the whole deck and the standard
  zone names (main/side/maybeboard/tokens) stay reserved.
- Board zones are created lazily on first use.
- getZoneObjFromName resolves custom names to their nested node so
  addCard and XML loading route cards into them. Unknown names keep
  creating legacy top-level zones.
- deleteNode keeps empty custom zones alive and only prunes empty
  board zones.
- New deck_list_zones test suite locks hash parity with flat decks,
  sideboard size accounting, maybeboard exclusion from plain export
  and native-format round-trips.

Took 17 minutes


Took 11 minutes

tests/deck_list_zones/CMakeLists.txt

@@ -0,0 +1,10 @@
+add_executable(deck_list_zones_test deck_list_zones_test.cpp)
+
+if(NOT GTEST_FOUND)
+  add_dependencies(deck_list_zones_test gtest)
+endif()
+
+target_link_libraries(
+  deck_list_zones_test libcockatrice_deck_list Threads::Threads ${GTEST_BOTH_LIBRARIES} ${TEST_QT_MODULES}
+)
+add_test(NAME deck_list_zones_test COMMAND deck_list_zones_test)