fix: return inner Logger from GetLogger for log.WithContext reuse

[guangxuewu]

fix: Ensure thread safety by eliminating lock copy in GetLogger

Description (what this PR does / why we need it):

Which issue(s) this PR fixes (resolves / be part of):

Other special notes for the reviewers:

[shenqidebaozi]

This pull request includes changes to improve the thread safety of the global logger and adds a new test to ensure the logger works correctly with context values.

Improvements to thread safety:

• log/global.go: Changed the lock field in loggerAppliance from sync.Mutex to sync.RWMutex to allow for concurrent read access.
• log/global.go: Updated the GetLogger function to use a read lock (RLock) when accessing the global logger, ensuring thread-safe read operations.

Enhancements to testing:

• log/global_test.go: Added a new test function TestContextWithGlobalLog to verify that the global logger correctly logs context values, ensuring the logger's functionality with context-based trace IDs.