- [x] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.
- [x] I have checked the [FAQ](https://github.com/apache/dubbo/blob/master/FAQ.md) of this repository and believe that this is not a duplicate.

### Environment

* Dubbo version: master
* Operating System version: windows
* Java version: 1.8

In ExtensionLoader, EXTENSION INSTANCES is a ConcurrentHashMap with a default size, and the extension class provided in Dubbo has exceeded 16. 
Start the program, it will expand at least twice. I think it is more appropriate to add an initial size of 64 here. 
Other places where ConcurrentHashMap is used should also pay attention to a suitable initial size
* like: ProtocolFilterWrapper, ProtocolListenerWrapper
     */
    private void cacheWrapperClass(Class<?> clazz) {
        if (cachedWrapperClasses == null) {
            cachedWrapperClasses = new ConcurrentHashSet<>();
        }
        cachedWrapperClasses.add(clazz);
    }
    /**
     * test if clazz is a wrapper class
     * <p>
     * which has Constructor with given class type as its only argument
     */
    private boolean isWrapperClass(Class<?> clazz) {
        try {
            clazz.getConstructor(type);
            return true;
        } catch (NoSuchMethodException e) {
            return false;
        }
    }
    @SuppressWarnings("deprecation")
    private String findAnnotationName(Class<?> clazz) {
        org.apache.dubbo.common.Extension extension = clazz.getAnnotation(org.apache.dubbo.common.Extension.class);
        if (extension != null) {
            return extension.value();
        }
        String name = clazz.getSimpleName();
        if (name.endsWith(type.getSimpleName())) {
            name = name.substring(0, name.length() - type.getSimpleName().length());