SPIGOT-5345: Add automatic library support

Example plugin.yml usage:
```
    libraries:
      - com.squareup.okhttp3:okhttp:4.9.0
```

Libraries will only be accessible to plugins and their transitive depends, allowing for multiple versions of the same library to be used by different plugins.

This feature is modeled on the parallel BungeeCord feature and intends to offer the same behaviour.
Although this is a preview feature, major changes to behaviour are not expected at this point.

With the exception of the issues described in SPIGOT-6419 it is not expected that this feature alters classloading behaviour, although some changes may be unavoidable.

By: md_5 <git@md-5.net>

paper-api/src/main/java/org/bukkit/plugin/PluginDescriptionFile.java

@@ -133,6 +133,10 @@ import org.yaml.snakeyaml.nodes.Tag;
  *     <td><code>api-version</code></td>
  *     <td>{@link #getAPIVersion()}</td>
  *     <td>The API version which this plugin was programmed against</td>
+ * </tr><tr>
+ *     <td><code>libraries</code></td>
+ *     <td>{@link #getLibraries() ()}</td>
+ *     <td>The libraries to be linked with this plugin</td>
  * </tr>
  * </table>
  * <p>
@@ -152,6 +156,8 @@ import org.yaml.snakeyaml.nodes.Tag;
  *main: com.captaininflamo.bukkit.inferno.Inferno
  *depend: [NewFire, FlameWire]
  *api-version: 1.13
+ *libraries:
+    - com.squareup.okhttp3:okhttp:4.9.0
  *
  *commands:
  *  flagrate:
@@ -247,6 +253,7 @@ public final class PluginDescriptionFile {
     private PermissionDefault defaultPerm = PermissionDefault.OP;
     private Set<PluginAwareness> awareness = ImmutableSet.of();
     private String apiVersion = null;
+    private List<String> libraries = ImmutableList.of();
 
     public PluginDescriptionFile(@NotNull final InputStream stream) throws InvalidDescriptionException {
         loadMap(asMap(YAML.get().load(stream)));
@@ -957,6 +964,22 @@ public final class PluginDescriptionFile {
         return apiVersion;
     }
 
+    /**
+     * Gets the libraries this plugin requires. This is a preview feature.
+     * <ul>
+     * <li>Libraries must be GAV specifiers and are loaded from Maven Central.
+     * </ul>
+     * <p>
+     * Example:<blockquote><pre>libraries:
+     *     - com.squareup.okhttp3:okhttp:4.9.0</pre></blockquote>
+     *
+     * @return required libraries
+     */
+    @NotNull
+    public List<String> getLibraries() {
+        return libraries;
+    }
+
     /**
      * @return unused
      * @deprecated unused
@@ -1127,6 +1150,20 @@ public final class PluginDescriptionFile {
             apiVersion = map.get("api-version").toString();
         }
 
+        if (map.get("libraries") != null) {
+            ImmutableList.Builder<String> contributorsBuilder = ImmutableList.<String>builder();
+            try {
+                for (Object o : (Iterable<?>) map.get("libraries")) {
+                    contributorsBuilder.add(o.toString());
+                }
+            } catch (ClassCastException ex) {
+                throw new InvalidDescriptionException(ex, "libraries are of wrong type");
+            }
+            libraries = contributorsBuilder.build();
+        } else {
+            libraries = ImmutableList.<String>of();
+        }
+
         try {
             lazyPermissions = (Map<?, ?>) map.get("permissions");
         } catch (ClassCastException ex) {
@@ -1201,6 +1238,10 @@ public final class PluginDescriptionFile {
             map.put("api-version", apiVersion);
         }
 
+        if (libraries != null) {
+            map.put("libraries", libraries);
+        }
+
         if (classLoaderOf != null) {
             map.put("class-loader-of", classLoaderOf);
         }