Add compatible module and rename groupId to org.apache.dubbo

[diecui1202]

What is the purpose of the change

Add compatible module and rename groupId to org.apache.dubbo

Brief changelog

1. Add single module named "dubbo-compatible", and support limited old extension, such Filter.
2. rename groupId to org.apache.dubbo

Verifying this change

All unit cases are pass

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[codecov-io]

Codecov Report

Merging #1952 into master will decrease coverage by 1.07%.
The diff coverage is 6.01%.

@@             Coverage Diff             @@
##             master   #1952      +/-   ##
===========================================
- Coverage     50.47%   49.4%   -1.08%     
+ Complexity     4746    4585     -161     
===========================================
  Files           518     548      +30     
  Lines         25424   24805     -619     
  Branches       4560    4394     -166     
===========================================
- Hits          12834   12256     -578     
- Misses        10641   10676      +35     
+ Partials       1949    1873      -76

Impacted Files	Coverage Δ	Complexity Δ
.../main/java/com/alibaba/dubbo/common/Constants.java	0% <0%> (ø)	0 <0> (?)
...ompatibleReferenceAnnotationBeanPostProcessor.java	0% <0%> (ø)	0 <0> (?)
.../alibaba/dubbo/common/serialize/Serialization.java	0% <0%> (ø)	0 <0> (?)
.../java/com/alibaba/dubbo/config/ProviderConfig.java	0% <0%> (ø)	0 <0> (?)
...ava/org/apache/dubbo/rpc/filter/GenericFilter.java	0% <0%> (ø)	0 <0> (ø)	⬇️
...g/apache/dubbo/rpc/proxy/AbstractProxyFactory.java	0% <0%> (ø)	0 <0> (ø)	⬇️
...a/dubbo/rpc/protocol/rest/support/ContentType.java	0% <0%> (ø)	0 <0> (?)
.../src/main/java/com/alibaba/dubbo/rpc/Exporter.java	0% <0%> (ø)	0 <0> (?)
...o/rpc/cluster/loadbalance/AbstractLoadBalance.java	0% <0%> (ø)	0 <0> (?)
...ory/annotation/CompatibleReferenceBeanBuilder.java	0% <0%> (ø)	0 <0> (?)
... and 89 more

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[kayyellow]

hi,
com.alibaba.dubbo.registry.RegistryFactory import the org.apache.dubbo.registry.Registry, but I extended the com.alibaba.dubbo.registry.Registry in version 2.5.4. So it cannot be compatible. Do u miss to import com.alibaba.dubbo.registry.Registry rather than org.apache.dubbo.registry.Registry ?

package com.alibaba.dubbo.registry;

import com.alibaba.dubbo.common.URL;
import org.apache.dubbo.registry.Registry;

/** @deprecated */
@deprecated
public interface RegistryFactory extends org.apache.dubbo.registry.RegistryFactory {
Registry getRegistry(URL var1);

default Registry getRegistry(org.apache.dubbo.common.URL url) {
    return this.getRegistry(new URL(url));
}

}

[kayyellow]

@beiwei30 @diecui1202 Hope to see the answer.