Rename EWYK The AdaptiveExecutionStrategy (#6353)

Rename EWYK to AdaptiveExecutionStrategy, which better represents the nature of the strategy.

Updated the documentation 
Refactored substrategy selection for code clarity.
Added notes about chaining strategies and thread starvation

Signed-off-by: Greg Wilkins <gregw@webtide.com>
Signed-off-by: Simone Bordet <simone.bordet@gmail.com>
Co-authored-by: Simone Bordet <simone.bordet@gmail.com>

jetty-http2/http2-common/src/main/java/org/eclipse/jetty/http2/HTTP2Connection.java

@@ -33,18 +33,14 @@
 import org.eclipse.jetty.util.component.LifeCycle;
 import org.eclipse.jetty.util.thread.AutoLock;
 import org.eclipse.jetty.util.thread.ExecutionStrategy;
-import org.eclipse.jetty.util.thread.TryExecutor;
-import org.eclipse.jetty.util.thread.strategy.EatWhatYouKill;
+import org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 public class HTTP2Connection extends AbstractConnection implements WriteFlusher.Listener, Connection.UpgradeTo
 {
     protected static final Logger LOG = LoggerFactory.getLogger(HTTP2Connection.class);
 
-    // TODO remove this once we are sure EWYK is OK for http2
-    private static final boolean PEC_MODE = Boolean.getBoolean("org.eclipse.jetty.http2.PEC_MODE");
-
     private final AutoLock lock = new AutoLock();
     private final Queue<Runnable> tasks = new ArrayDeque<>();
     private final HTTP2Producer producer = new HTTP2Producer();
@@ -64,9 +60,7 @@ public HTTP2Connection(ByteBufferPool byteBufferPool, Executor executor, EndPoin
         this.parser = parser;
         this.session = session;
         this.bufferSize = bufferSize;
-        if (PEC_MODE)
-            executor = new TryExecutor.NoTryExecutor(executor);
-        this.strategy = new EatWhatYouKill(producer, executor);
+        this.strategy = new AdaptiveExecutionStrategy(producer, executor);
         LifeCycle.start(strategy);
         parser.init(ParserListener::new);
     }

jetty-io/src/main/java/org/eclipse/jetty/io/ManagedSelector.java

@@ -49,7 +49,7 @@
 import org.eclipse.jetty.util.thread.AutoLock;
 import org.eclipse.jetty.util.thread.ExecutionStrategy;
 import org.eclipse.jetty.util.thread.Scheduler;
-import org.eclipse.jetty.util.thread.strategy.EatWhatYouKill;
+import org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -95,7 +95,7 @@ public ManagedSelector(SelectorManager selectorManager, int id)
         _id = id;
         SelectorProducer producer = new SelectorProducer();
         Executor executor = selectorManager.getExecutor();
-        _strategy = new EatWhatYouKill(producer, executor);
+        _strategy = new AdaptiveExecutionStrategy(producer, executor);
         addBean(_strategy, true);
     }