[dubbo-2029]: upgrade netty4 to the latest release and make it the default option for transporter

[beiwei30]

…lt option for transporter

What is the purpose of the change

issue#2029: upgrade netty4 to the latest release and make it the default option for transporter

Brief changelog

dependencies-bom/pom.xml
dubbo-common/src/main/java/org/apache/dubbo/common/Constants.java
dubbo-config/dubbo-config-api/pom.xml
dubbo-config/dubbo-config-spring/pom.xml
dubbo-demo/dubbo-demo-consumer/pom.xml
dubbo-demo/dubbo-demo-provider/pom.xml
dubbo-monitor/dubbo-monitor-default/pom.xml
dubbo-registry/dubbo-registry-default/pom.xml
dubbo-remoting/dubbo-remoting-api/src/main/java/org/apache/dubbo/remoting/Transporter.java
dubbo-remoting/dubbo-remoting-netty/src/test/java/org/apache/dubbo/remoting/exchange/support/header/HeartbeatHandlerTest.java
dubbo-remoting/dubbo-remoting-netty/src/test/java/org/apache/dubbo/remoting/transport/netty/ClientReconnectTest.java
dubbo-remoting/dubbo-remoting-netty/src/test/java/org/apache/dubbo/remoting/transport/netty/NettyClientTest.java
dubbo-remoting/dubbo-remoting-netty4/src/main/java/org/apache/dubbo/remoting/transport/netty4/NettyClientHandler.java
dubbo-remoting/dubbo-remoting-p2p/pom.xml
dubbo-rpc/dubbo-rpc-dubbo/pom.xml
dubbo-rpc/dubbo-rpc-thrift/pom.xml

Verifying this change

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[codecov-io]

Codecov Report

Merging #2049 into master will increase coverage by 0.83%.
The diff coverage is 12.5%.

@@             Coverage Diff              @@
##             master    #2049      +/-   ##
============================================
+ Coverage     52.19%   53.02%   +0.83%     
- Complexity     4963     4986      +23     
============================================
  Files           568      568              
  Lines         25453    25460       +7     
  Branches       4486     4487       +1     
============================================
+ Hits          13285    13501     +216     
+ Misses        10144     9913     -231     
- Partials       2024     2046      +22

Impacted Files	Coverage Δ	Complexity Δ
...bbo/remoting/transport/netty/NettyTransporter.java	100% <ø> (ø)	3 <0> (ø)	⬇️
...bo/remoting/transport/netty4/NettyTransporter.java	100% <ø> (ø)	3 <0> (ø)	⬇️
.../remoting/transport/netty4/NettyClientHandler.java	58.33% <12.5%> (-14.09%)	5 <0> (ø)
...ache/dubbo/remoting/p2p/support/AbstractGroup.java	45.45% <0%> (-11.37%)	7% <0%> (-1%)
...he/dubbo/remoting/transport/netty/NettyClient.java	72.88% <0%> (-8.48%)	12% <0%> (-1%)
...rpc/protocol/dubbo/telnet/InvokeTelnetHandler.java	51.89% <0%> (-3.8%)	11% <0%> (-2%)
...dubbo/rpc/protocol/dubbo/CallbackServiceCodec.java	77.2% <0%> (-1.48%)	29% <0%> (ø)
.../dubbo/remoting/transport/netty4/NettyChannel.java	65% <0%> (-1.25%)	22% <0%> (-1%)
.../apache/dubbo/rpc/protocol/injvm/InjvmInvoker.java	69.23% <0%> (+15.38%)	3% <0%> (+1%)	⬆️
.../apache/dubbo/rpc/protocol/thrift/ThriftUtils.java	91.8% <0%> (+16.39%)	8% <0%> (+2%)	⬆️
... and 3 more

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[chickenlj]

Agree to change the default transporter to netty4.

Only one thing to note: this change is not transparent to the user, they should guarantee [netty 4](https://github.com/netty/netty) in the classpath, which is not always satisfied since their projects may rely on netty3 by default. But I think it's ok, a release note for incompatible upgrade is enough.

[chickenlj]

To continue use netty, how about this way:

based on your PR, add the following items,
For netty4/Transporter

netty=org.apache.dubbo.remoting.transport.netty4.NettyTransporter
netty4=org.apache.dubbo.remoting.transport.netty4.NettyTransporter

And

For netty3/Transporter

netty3=org.apache.dubbo.remoting.transport.netty.NettyTransporter

[chickenlj]

Keep netty no changed

@SPI("netty")
 public interface Transporter {

[zonghaishang]

Perhaps the server should be removed and passed to the client.

[chickenlj]

@zonghaishang Agree to remove server from the client, and this can be achieved within this issue #2030