Finish converting most of the undeprecated api to jspecify

patches/api/Missing-Entity-API.patch

@@ -23,12 +23,13 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +package io.papermc.paper.entity;
 +
 +import org.bukkit.entity.Fish;
-+import org.jetbrains.annotations.NotNull;
-+import org.jetbrains.annotations.Nullable;
++import org.jspecify.annotations.NullMarked;
++import org.jspecify.annotations.Nullable;
 +
 +/**
 + * Represents a fish that can school with other fish.
 + */
++@NullMarked
 +public interface SchoolableFish extends Fish {
 +
 +    /**
@@ -36,7 +37,7 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +     *
 +     * @param leader fish to follow
 +     */
-+    void startFollowing(@NotNull SchoolableFish leader);
++    void startFollowing(SchoolableFish leader);
 +
 +    /**
 +     * Causes the fish to stop following their current
@@ -63,8 +64,7 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +     *
 +     * @return following fish
 +     */
-+    @Nullable
-+    SchoolableFish getSchoolLeader();
++    @Nullable SchoolableFish getSchoolLeader();
 +
 +}
 diff --git a/src/main/java/org/bukkit/entity/AbstractHorse.java b/src/main/java/org/bukkit/entity/AbstractHorse.java