feat: add GetLogLevel and GetAllLogLevels

[SgtPooki]

Add Log Level Retrieval Functionality

Summary

Added functionality to track and retrieve current log levels (global and per-subsystem) to improve debugging capabilities.

Related ipfs/kubo#10882
Fixes #159

Changes

New Functions

• GetLogLevel(names string) (LogLevel, error)

  • Returns current default level when called with "" or "*"
  • Returns specific subsystem level when called with subsystem name
  • Returns ErrNoSuchLogger for non-existent subsystems

• GetAllLogLevels() map[string]LogLevel

  • Returns map of all current log levels
  • Includes "*" key for default/global level
  • Shows all registered subsystem levels

Key Features

• Thread-safe - Uses existing loggerMutex for concurrent access
• Real-time - Reflects dynamic changes made via SetLogLevel()
• Consistent API - Follows existing naming conventions and patterns

Usage Examples

// Get default level
level, err := log.GetLogLevel("*")

// Get specific subsystem level
httpLevel, err := log.GetLogLevel("http")

// Get all current levels
allLevels := log.GetAllLogLevels()
fmt.Printf("Default: %v\n", allLevels["*"])

Testing

Added comprehensive tests covering:

• Default level retrieval ("", "*")
• Subsystem level retrieval (existing/non-existing)
• Dynamic level changes
• Modifying the returned map does not affect internal state

[SgtPooki]

self review

[SgtPooki]

I posted some questions on the Kubo PR about how we want to handle global going forward. I didn't want to change it in this PR by default, but if we have updated the global setting, it should make sure new loggers are using that setting rather than the “default” that, currently in this PR, is only the basic starting level for logs..

But, I guess it could be viewed as better either way.

[SgtPooki]

self review

[gammazero]

Suggested change

	return zapcore.Level(LogLevel(lvl.Level())).String(), nil
	return lvl.Level().String(), nil

[gammazero]

Suggested change

	result[name] = zapcore.Level(LogLevel(level.Level())).String()
	result[name] = level.Level().String()