Core/Misc: added more fallthrough attributes and added some missing breaks reported by CI

src/server/game/Entities/Unit/Unit.cpp

@@ -7131,7 +7131,7 @@ float Unit::GetUnitSpellCriticalChance(Unit* victim, SpellInfo const* spellProto
                 default:
                     return 0.0f;
             }
-        // Do not add a break here, case fallthrough is intentional! Adding a break will make above spells unable to crit.
+        [[fallthrough]]; // fallthrough is intentional! Adding a break will make above spells unable to crit.
         case SPELL_DAMAGE_CLASS_MAGIC:
         {
             if (schoolMask & SPELL_SCHOOL_MASK_NORMAL)
@@ -7307,7 +7307,7 @@ float Unit::GetUnitSpellCriticalChance(Unit* victim, SpellInfo const* spellProto
                         break;
                 }
             }
-            /* fallthrough - Calculate critical strike chance for both Ranged and Melee spells*/
+            [[fallthrough]]; // fallthrough - Calculate critical strike chance for both Ranged and Melee spells
         case SPELL_DAMAGE_CLASS_RANGED:
         {
             if (victim)