Callbacks Log does not implement the new methods

[terwey]

The new methods for callbacks are not implemented in the LogHandler in tag v0.1.4

I am sure this was missed because of the following composition and thus the static assertion is moot.

langchaingo/callbacks/log.go

Lines 12 to 17 in 7601dc3

	// LogHandler is a callback handler that prints to the standard output.
	type LogHandler struct {
	SimpleHandler
	}
	var _ Handler = LogHandler{}

These methods are missing:

langchaingo/callbacks/callbacks.go

Lines 17 to 18 in 7601dc3

	HandleLLMGenerateContentStart(ctx context.Context, ms []llms.MessageContent)
	HandleLLMGenerateContentEnd(ctx context.Context, res *llms.ContentResponse)

langchaingo/callbacks/callbacks.go

Line 30 in 7601dc3

HandleStreamingFunc(ctx context.Context, chunk []byte)