Support Spring Boot 4.0 bootstrap context package relocation

[Copilot]

What's the purpose of this PR

Spring Boot 4.0 relocated bootstrap context classes from org.springframework.boot to org.springframework.boot.bootstrap. This causes NoSuchMethodError on both ApplicationStartingEvent.getBootstrapContext() and ConfigDataLoaderContext.getBootstrapContext() when using apollo-client-config-data with Spring Boot 4.0.

Caused by: java.lang.NoSuchMethodError: 'org.springframework.boot.ConfigurableBootstrapContext 
  org.springframework.boot.context.event.ApplicationStartingEvent.getBootstrapContext()'

Caused by: java.lang.NoSuchMethodError: 'org.springframework.boot.ConfigurableBootstrapContext 
  org.springframework.boot.context.config.ConfigDataLoaderContext.getBootstrapContext()'

This PR adds a reflection-based compatibility layer to support both Spring Boot 2.x/3.x and 4.x.

Which issue(s) this PR fixes:

Brief changelog

• Add BootstrapRegistryHelper utility that detects Spring Boot version at runtime and uses reflection to invoke bootstrap context methods from either package location
• Handle both ApplicationStartingEvent.getBootstrapContext() and ConfigDataLoaderContext.getBootstrapContext() via reflection
• Update all 7 files using ConfigurableBootstrapContext or BootstrapRegistry.InstanceSupplier to use Object type with helper methods:
  • ApolloSpringApplicationRegisterListener
  • ApolloConfigDataLoader
  • ApolloConfigDataLoaderInitializer
  • ApolloClientExtensionInitializeFactory
  • ApolloClientLongPollingExtensionInitializer
  • ApolloClientWebsocketExtensionInitializer
  • ApolloClientWebClientCustomizerFactory

Follow this checklist to help us incorporate your contribution quickly and easily:

• Read the Contributing Guide before making this pull request.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit tests to verify the code.
• Run mvn clean test to make sure this pull request doesn't break anything.
• Update the CHANGES log.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Support Spring Boot 4.0</issue_title>
<issue_description>将 com.ctrip.framework.apollo:apollo-client-config-data:2.4.0 与 spring-boot 4.0.0 一起使用， 启动报错 java.lang.NoSuchMethodError:

Caused by: java.lang.NoSuchMethodError: 'org.springframework.boot.ConfigurableBootstrapContext org.springframework.boot.context.event.ApplicationStartingEvent.getBootstrapContext()'
	at com.ctrip.framework.apollo.config.data.listener.ApolloSpringApplicationRegisterListener.onApplicationEvent(ApolloSpringApplicationRegisterListener.java:33)
	at com.ctrip.framework.apollo.config.data.listener.ApolloSpringApplicationRegisterListener.onApplicationEvent(ApolloSpringApplicationRegisterListener.java:28)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:180)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:173)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:151)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:133)
	at org.springframework.boot.context.event.EventPublishingRunListener.multicastInitialEvent(EventPublishingRunListener.java:137)

Spring Boot 4.0 包名变了：
org.springframework.boot.ConfigurableBootstrapContext
->
org.springframework.boot.bootstrap.ConfigurableBootstrapContext

https://github.com/spring-projects/spring-boot/releases/tag/v4.0.0
</issue_description>

<agent_instructions>Design a solution enabling apollo-client to support both Spring Boot 4.x and earlier versions.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Support Spring Boot 4.0 #114

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[nobodyiam]

@copilot

There are further issues that need to be fixed.

Exception in thread "main" java.lang.IllegalStateException: java.lang.NoSuchMethodError: 'org.springframework.boot.ConfigurableBootstrapContext org.springframework.boot.context.config.ConfigDataLoaderContext.getBootstrapContext()'
at org.springframework.boot.SpringApplication.handleRunFailure(SpringApplication.java:836)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:331)
at org.springframework.boot.builder.SpringApplicationBuilder.run(SpringApplicationBuilder.java:154)
at com.apolloconfig.apollo.demo.springboot.SpringBootSampleApplication.main(SpringBootSampleApplication.java:36)
Caused by: java.lang.NoSuchMethodError: 'org.springframework.boot.ConfigurableBootstrapContext org.springframework.boot.context.config.ConfigDataLoaderContext.getBootstrapContext()'
at com.ctrip.framework.apollo.config.data.importer.ApolloConfigDataLoader.load(ApolloConfigDataLoader.java:57)
at com.ctrip.framework.apollo.config.data.importer.ApolloConfigDataLoader.load(ApolloConfigDataLoader.java:43)
at org.springframework.boot.context.config.ConfigDataLoaders.load(ConfigDataLoaders.java:100)
at org.springframework.boot.context.config.ConfigDataImporter.load(ConfigDataImporter.java:133)
at org.springframework.boot.context.config.ConfigDataImporter.resolveAndLoad(ConfigDataImporter.java:88)
at org.springframework.boot.context.config.ConfigDataEnvironmentContributors.withProcessedImports(ConfigDataEnvironmentContributors.java:130)
at org.springframework.boot.context.config.ConfigDataEnvironment.processWithProfiles(ConfigDataEnvironment.java:322)
at org.springframework.boot.context.config.ConfigDataEnvironment.processAndApply(ConfigDataEnvironment.java:241)

[Copilot]

@copilot

There are further issues that need to be fixed.
...

Fixed in commit 5f54fdf. Added reflection-based method getBootstrapContext(ConfigDataLoaderContext) to BootstrapRegistryHelper and updated ApolloConfigDataLoader to use it. The ConfigDataLoaderContext.getBootstrapContext() method also has a different return type in Spring Boot 4.0 (ConfigurableBootstrapContext moved to org.springframework.boot.bootstrap package), so it needed the same reflection treatment as ApplicationStartingEvent.getBootstrapContext().

[nobodyiam]

@copilot This pr looks good to me. Please update the CHANGES.md.

[nobodyiam]

LGTM