chore(gax-grpc): add comments and remove magic numbers for resize delta

Author: lqiu96

sdk-platform-java/gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/ChannelPool.java

@@ -84,6 +84,8 @@ class ChannelPool extends ManagedChannel {
   private final AtomicInteger indexTicker = new AtomicInteger();
   private final String authority;
 
+  // Tracks the number of consecutive resize cycles where a resize actually occurred (either expand or shrink).
+  // Used to detect repeated resizing activity and log a warning.
   private int consecutiveResizes = 0;
 
   static ChannelPool create(

sdk-platform-java/gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/ChannelPoolSettings.java

@@ -141,7 +141,7 @@ public static ChannelPoolSettings staticallySized(int size) {
         .setMaxRpcsPerChannel(Integer.MAX_VALUE)
         .setMinChannelCount(size)
         .setMaxChannelCount(size)
-        .setMaxResizeDelta(Math.min(2, size))
+        .setMaxResizeDelta(Math.min(MAX_RESIZE_DELTA, size))
         .build();
   }
 
@@ -153,7 +153,7 @@ public static Builder builder() {
         .setMinRpcsPerChannel(0)
         .setMaxRpcsPerChannel(Integer.MAX_VALUE)
         .setPreemptiveRefreshEnabled(false)
-        .setMaxResizeDelta(2);
+        .setMaxResizeDelta(MAX_RESIZE_DELTA);
   }
 
   @AutoValue.Builder