[3.0] Extract DubboSpringInitializer and support customize initialization

[kylixs]

What is the purpose of the change

Extract DubboSpringInitializer and support customize initialization.

Brief changelog

[codecov-commenter]

Codecov Report

Merging #8495 (f7898f7) into 3.0 (b5e65a6) will decrease coverage by 0.01%.
The diff coverage is 74.07%.

@@             Coverage Diff              @@
##                3.0    #8495      +/-   ##
============================================
- Coverage     62.85%   62.83%   -0.02%     
- Complexity      311      312       +1     
============================================
  Files          1113     1115       +2     
  Lines         46660    46683      +23     
  Branches       7020     7022       +2     
============================================
+ Hits          29326    29332       +6     
- Misses        14077    14090      +13     
- Partials       3257     3261       +4     

Impacted Files	Coverage Δ
...he/dubbo/config/spring/util/SpringCompatUtils.java	28.26% <40.00%> (-0.32%)	⬇️
...ring/context/DubboSpringInitializationContext.java	75.00% <75.00%> (ø)
.../config/spring/context/DubboSpringInitializer.java	80.00% <80.00%> (ø)
...ontext/annotation/DubboComponentScanRegistrar.java	100.00% <100.00%> (ø)
.../annotation/DubboConfigConfigurationRegistrar.java	100.00% <100.00%> (ø)
...bo/config/spring/schema/DubboNamespaceHandler.java	100.00% <100.00%> (ø)
...in/java/org/apache/dubbo/common/utils/JVMUtil.java	81.13% <0.00%> (-11.33%)	⬇️
.../apache/dubbo/remoting/transport/AbstractPeer.java	60.86% <0.00%> (-4.35%)	⬇️
...pache/dubbo/config/spring/util/DubboBeanUtils.java	82.92% <0.00%> (-2.44%)	⬇️
...ache/dubbo/rpc/protocol/AbstractProxyProtocol.java	58.33% <0.00%> (-2.39%)	⬇️
... and 6 more

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