Do not submit profile lookups to worldgen threads

They block. On network I/O.

If enough tasks are submitted the server will eventually stall
out due to a sync load, as the worldgen threads will be
stalling on profile lookups.

paper-server/patches/sources/net/minecraft/server/players/GameProfileCache.java.patch

@@ -51,6 +51,15 @@
          }
  
          return optional;
+@@ -167,7 +169,7 @@
+             } else {
+                 CompletableFuture<Optional<GameProfile>> completablefuture1 = CompletableFuture.supplyAsync(() -> {
+                     return this.get(username);
+-                }, Util.backgroundExecutor().forName("getProfile")).whenCompleteAsync((optional, throwable) -> {
++                }, Util.PROFILE_EXECUTOR).whenCompleteAsync((optional, throwable) -> { // Paper - don't submit BLOCKING PROFILE LOOKUPS to the world gen thread
+                     this.requests.remove(username);
+                 }, this.executor);
+ 
 @@ -208,7 +210,7 @@
  
              label54: