- [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
lifecycle.initialize();
        }
    }
    /**
     * get properties name for setter, for instance: setVersion, return "version"
     * <p>
     * return "", if setter name with length less than 3
     */
    private String getSetterProperty(Method method) {
        return method.getName().length() > 3 ? method.getName().substring(3, 4).toLowerCase() + method.getName().substring(4) : "";
    }
    /**
     * return true if and only if:
     * <p>
     * 1, public
     * <p>
     * 2, name starts with "set"
     * <p>
     * 3, only has one parameter
     */
    private boolean isSetter(Method method) {
        return method.getName().startsWith("set")
                && method.getParameterTypes().length == 1
                && Modifier.isPublic(method.getModifiers());
    }
    private Class<?> getExtensionClass(String name) {
        if (type == null) {
            throw new IllegalArgumentException("Extension type == null");
        }
        if (name == null) {