Remove lifetime mess, replace a lot of code with Arc instead of borrows.

This cleans up the codebase massively, and allows me to maintain some semblance of sanity.

src/static_data/natures.rs

@@ -1,3 +1,5 @@
+use std::sync::Arc;
+
 use hashbrown::HashMap;
 
 use crate::static_data::Statistic;
@@ -60,7 +62,7 @@ impl Nature {
 #[derive(Debug)]
 pub struct NatureLibrary {
     /// The underlying data structure.
-    map: HashMap<StringKey, Nature>,
+    map: HashMap<StringKey, Arc<Nature>>,
 }
 
 impl NatureLibrary {
@@ -73,20 +75,20 @@ impl NatureLibrary {
 
     /// Adds a new nature with name to the library.
     pub fn load_nature(&mut self, name: StringKey, nature: Nature) {
-        self.map.insert(name, nature);
+        self.map.insert(name, Arc::new(nature));
     }
 
     /// Gets a nature by name.
-    pub fn get_nature(&self, key: &StringKey) -> Option<&Nature> {
+    pub fn get_nature(&self, key: &StringKey) -> Option<&Arc<Nature>> {
         self.map.get(key)
     }
 
     /// Finds a nature name by nature.
-    pub fn get_nature_name(&self, nature: &Nature) -> StringKey {
+    pub fn get_nature_name(&self, nature: &Arc<Nature>) -> StringKey {
         for kv in &self.map {
             // As natures can't be copied, and should always be the same reference as the value
             // in the map, we just compare by reference.
-            if std::ptr::eq(kv.1, nature) {
+            if Arc::ptr_eq(kv.1, nature) {
                 return kv.0.clone();
             }
         }