[OSPP]Add more observability in apollo config client

[Rawven]

What's the purpose of this PR

discussions OSPP2024
test cases Test

Which issue(s) this PR fixes:

Issue

Brief changelog

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Summary by CodeRabbit

Summary by CodeRabbit

• New Features

  • Added a new entry in the release notes for Apollo Java version 2.4.0: "Add more observability in apollo config client."
  • Introduced several monitoring APIs for exceptions, namespaces, bootstrap arguments, and thread pools, enhancing visibility into system performance.
  • Launched the ApolloClientBootstrapArgsMonitorApi, ApolloClientNamespaceMonitorApi, and ApolloClientThreadPoolMonitorApi to manage configuration parameters and resource metrics.
  • Enhanced monitoring capabilities with structured logging for metrics and events.
  • Added a ConfigMonitorInitializer class to facilitate the setup of monitoring components.

• Improvements

  • Enhanced error handling in various services by using defined constants for logging.
  • Updated metrics collection mechanisms to track configuration loading durations and exception occurrences efficiently.
  • Added new configuration properties for improved control over monitoring settings.

• Bug Fixes

  • Refined logging and error tracking to ensure consistency and accuracy in reporting metrics.

• Tests

  • Introduced comprehensive unit tests for newly added monitoring features and functionality.
  • Implemented tests for the ApolloClientMonitorContext, ApolloClientMetricsExporter, and other monitoring components to ensure correct functionality.