Allow config of IO and acceptor threads in proxy (apache#14054)

* Allow config of IO and acceptor threads in proxy

Previously, the Pulasr Proxy did not allow configuration of the number
of IO threads and acceptor threads in the proxy.

These options can be very important to tune, as is tuneable in the
broker, so this change simply matches the brokers perspective.

Also, we increase the default number of IO threads to 2x number of
processors instead of 1x, as in a single CPU config, it still makes
sense to have 2 threads, at least for now, where some blocking
operatings can happen (such as authn/authz plugins)

* fix checkstyle

(cherry picked from commit f455418)

pulsar-proxy/src/main/java/org/apache/pulsar/proxy/server/ProxyConfiguration.java

@@ -495,6 +495,20 @@ public class ProxyConfiguration implements PulsarConfiguration {
     )
     private int httpNumThreads = Math.max(8, 2 * Runtime.getRuntime().availableProcessors());
 
+    @FieldContext(
+            category = CATEGORY_SERVER,
+            doc = "Number of threads to use for Netty IO."
+                    + " Default is set to `2 * Runtime.getRuntime().availableProcessors()`"
+    )
+    private int numIOThreads = 2 * Runtime.getRuntime().availableProcessors();
+
+    @FieldContext(
+            category = CATEGORY_SERVER,
+            doc = "Number of threads to use for Netty Acceptor."
+                    + " Default is set to `1`"
+    )
+    private int numAcceptorThreads = 1;
+
     @Deprecated
     @FieldContext(
             category = CATEGORY_PLUGIN,

pulsar-proxy/src/main/java/org/apache/pulsar/proxy/server/ProxyService.java

@@ -101,8 +101,6 @@ public class ProxyService implements Closeable {
 
     private final ScheduledExecutorService statsExecutor;
 
-    private static final int numThreads = Runtime.getRuntime().availableProcessors();
-
     static final Gauge activeConnections = Gauge
             .build("pulsar_proxy_active_connections", "Number of connections currently active in the proxy").create()
             .register();
@@ -143,8 +141,10 @@ public ProxyService(ProxyConfiguration proxyConfig,
         } else {
             proxyLogLevel = 0;
         }
-        this.acceptorGroup = EventLoopUtil.newEventLoopGroup(1, false, acceptorThreadFactory);
-        this.workerGroup = EventLoopUtil.newEventLoopGroup(numThreads, false, workersThreadFactory);
+        this.acceptorGroup = EventLoopUtil.newEventLoopGroup(proxyConfig.getNumAcceptorThreads(),
+                false, acceptorThreadFactory);
+        this.workerGroup = EventLoopUtil.newEventLoopGroup(proxyConfig.getNumIOThreads(),
+                false, workersThreadFactory);
         this.authenticationService = authenticationService;
 
         statsExecutor = Executors