Add Core function to logp.Logger to allow access to backing zapcore.Core.

[blakerouse]

What does this PR do?

Adds the ability to retrieve the zapcore.Core from the logp.Logger. This allows the ability to write entries directly into the logger bypassing any log levels settings.

Why is it important?

This is needed for the work on elastic/elastic-agent#221. The io.Writer connected to stdout and stderr from the spawned subprocesses will read the output from the process and output it directly to the zapcore.Core. That is required because each component and unit can have its own log level different from the Elastic Agent log level. Because of that design it requires that log messages bypass the log level settings for the logger used by Elastic Agent.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• [ ] I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.md

Related issues

• Closes Elastic Agent should aggregate the log from his subprocesses elastic-agent#221

[elasticmachine]

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• Start Time: 2022-11-05T17:20:59.849+0000

• Duration: 9 min 24 sec

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Failed	0
Passed	723
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Total	728

🤖 GitHub comments

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[rdner]

I wonder if it would be better to define a type alias like it's done with the zap.Option:

elastic-agent-libs/logp/logger.go

Lines 27 to 28 in 89215ad

	// LogOption configures a Logger.
	type LogOption = zap.Option

I don't know how far we want to go exposing the zap types in our library. I see that the Logger struct just has zap types directly:

elastic-agent-libs/logp/logger.go

Lines 30 to 34 in 89215ad

	// Logger logs messages to the configured output.
	type Logger struct {
	logger *zap.Logger
	sugar *zap.SugaredLogger
	}

[blakerouse]

Don't see a need to hide it. It is zap and zapcore under the hood and the go.mod for any project that imports elastic-agent-libs will show zap and zapcore.

[rdner]

It would rather an abstraction should we decide to switch from zap to something else. I guess that's the point. But I'm okay with this.