Refactor quest saving, update Galaxy-API version

Quest saving logic was abstracted into a saveQuest method in the Quest class to avoid redundancy. This change was reflected in OtherQuest, MineQuest, BreedMobsQuest, KillMobsQuest and CollectDropsQuest classes. Additionally, the Galaxy-API version was updated in the build.gradle.kts file.

build.gradle.kts

@@ -44,6 +44,6 @@ tasks {
 }
 
 dependencies {
-    compileOnly("com.alttd:Galaxy-API:1.19-R0.1-SNAPSHOT")
+    compileOnly("com.alttd:Galaxy-API:1.20.4-R0.1-SNAPSHOT")
     compileOnly("com.alttd.datalock:api:1.1.0-SNAPSHOT")
 }