增强线程池：在请求量阶段性出现高峰时使用
特性：cores线程全部使用的情况下，优先创建线程（总数不会超过max），当max个线程全都在忙的情况下，才将任务放入队列。请求量下降时，线程池会自动维持cores个线程，多余的线程退出。

增强线程池：在请求量阶段性出现高峰时使用
特性：cores线程全部使用的情况下，优先创建线程（总数不会超过max），当max个线程全都在忙的情况下，才将任务放入队列。请求量下降时，线程池会自动维持cores个线程，多余的线程退出。

long 初始化赋值时，小写l改为大写L防止误读

# Conflicts:
#	dubbo-common/src/main/java/com/alibaba/dubbo/common/serialize/support/dubbo/Builder.java
#	dubbo-common/src/main/java/com/alibaba/dubbo/common/serialize/support/dubbo/GenericDataInput.java
#	dubbo-common/src/main/java/com/alibaba/dubbo/common/serialize/support/dubbo/GenericDataOutput.java
#	dubbo-common/src/main/java/com/alibaba/dubbo/common/serialize/support/dubbo/GenericObjectInput.java
#	dubbo-common/src/main/java/com/alibaba/dubbo/common/serialize/support/dubbo/GenericObjectOutput.java
#	dubbo-common/src/main/java/com/alibaba/dubbo/common/serialize/support/json/JsonObjectInput.java
#	dubbo-common/src/main/java/com/alibaba/dubbo/common/serialize/support/json/JsonObjectOutput.java
#	dubbo-common/src/main/java/com/alibaba/dubbo/common/serialize/support/json/JsonSerialization.java
#	dubbo-filter/dubbo-filter-cache/src/main/java/com/alibaba/dubbo/cache/support/AbstractCacheFactory.java
#	dubbo-remoting/dubbo-remoting-grizzly/src/main/test/com/alibaba/dubbo/remoting/transport/grizzly/GrizzlyTransporterTest.java
#	dubbo-rpc/dubbo-rpc-dubbo/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/DubboInvoker.java
#	dubbo-rpc/dubbo-rpc-dubbo/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/FutureAdapter.java
#	dubbo-rpc/dubbo-rpc-dubbo/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/ReferenceCountExchangeClient.java
#	dubbo-rpc/dubbo-rpc-dubbo/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/filter/FutureFilter.java
#	dubbo-rpc/dubbo-rpc-dubbo/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/filter/TraceFilter.java
#	dubbo-rpc/dubbo-rpc-dubbo/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/status/ServerStatusChecker.java
#	dubbo-rpc/dubbo-rpc-dubbo/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/status/ThreadPoolStatusChecker.java
#	dubbo-rpc/dubbo-rpc-dubbo/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/telnet/ChangeTelnetHandler.java
#	dubbo-rpc/dubbo-rpc-dubbo/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/telnet/CountTelnetHandler.java
#	dubbo-rpc/dubbo-rpc-dubbo/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/telnet/CurrentTelnetHandler.java
#	dubbo-rpc/dubbo-rpc-dubbo/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/telnet/InvokeTelnetHandler.java
#	dubbo-rpc/dubbo-rpc-dubbo/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/telnet/ListTelnetHandler.java
#	dubbo-rpc/dubbo-rpc-dubbo/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/telnet/PortTelnetHandler.java
#	dubbo-rpc/dubbo-rpc-dubbo/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/telnet/TraceTelnetHandler.java
#	dubbo-serialization/dubbo-serialization-fastjson/src/main/java/com/alibaba/dubbo/common/serialize/fastjson/FastJsonObjectInput.java
#	dubbo-serialization/dubbo-serialization-fastjson/src/main/java/com/alibaba/dubbo/common/serialize/fastjson/FastJsonObjectOutput.java
#	dubbo-serialization/dubbo-serialization-fastjson/src/main/java/com/alibaba/dubbo/common/serialize/fastjson/FastJsonSerialization.java
#	dubbo-serialization/dubbo-serialization-hessian2/src/main/java/com/alibaba/dubbo/common/serialize/hessian2/Hessian2Serialization.java
#	dubbo-serialization/dubbo-serialization-jdk/src/main/java/com/alibaba/dubbo/common/serialize/java/CompactedJavaSerialization.java
#	dubbo-serialization/dubbo-serialization-jdk/src/main/java/com/alibaba/dubbo/common/serialize/java/JavaSerialization.java

# Conflicts:
#	dubbo-common/src/main/resources/META-INF/dubbo/internal/com.alibaba.dubbo.common.threadpool.ThreadPool
#	dubbo-common/src/test/java/com/alibaba/dubbo/common/utils/ConfigUtilsTest.java

* Used in RpcContext`s LOCAL field.
* Faster get than the traditional ThreadLocal

Fix bug in method removeAll