Misc logging cleanup + commentary

[jtcohen6]

I played around with the logging module this morning from an end-user perspective. It was a lot of fun! There are some fixes we should definitely merge; some questions are open for discussion. I tried to keep the commits separate + clean, so we could split up and cherry-pick accordingly. This is all in the interest of making dbt look + feel "like dbt" by v1 final.

Critical fixes

• Minor Cleanup of Structured Logging Module #4266 turned on JSON-formatted logging everywhere all the time, except for the legacy logger. Re-enable the choice between create_json_log_line and create_text_log_line based on this.format_json

Touch-ups + cosmetic fixes

• For events whose messages were prefixed with \n, instead precede them with fire_event(EmptyLine()). This is much cleaner to look at, since all (non-wrapped) log lines get the same frontmatter (timestamp + log level)
• I happened to notice that ConcurrencyLine could be more structured (unless there's a good reason why it wasn't)
• If we're going to include log levels on the CLI (more on this below), disable duplicative WARNING prefixes in messages / formatted via warning_tag

Commentary

• Log levels: These are amazing to have in the File. I find they add a bit too much noise on the CLI. I'd be happy with either (a) turning them off for CLI logging, or (b) colorizing warn/yellow + error/red to raise the signal from the noise. (Also, I believe Minor Cleanup of Structured Logging Module #4266 removed width-fixing for log levels, so I added that back in.)
• Colorization: Ideally, we'd have a way to turn this off for both File + JSON-formatted logging. This would require a little bit of plumbing: dbt.ui.color would need information from the events module, beyond just flags.USE_COLORS. Since color methods are mostly called in messages defined on event classes, I wonder if this could work by adding a use_color(self) -> bool method to the File + Cli base types, and reimplementing the color methods to check self.use_color (where self = event class).
• EmptyLine: Just like colorization, this is great for CLI + text formatting, but we'd ideally have a way to turn it off for File or JSON logging. (This is what logbook accomplished via the TextOnly() wrapper; I realize I was a bit inconsistent in whether I used this.)

Broadly, I find that I want:

• color, concision, clean spacing on the CLI
• colorless + compact verbosity in the File + JSON-formatted

Checklist

• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have updated the CHANGELOG.md and added information about my change

[jtcohen6]

@nathaniel-may @emmyoop @iknox-fa Tagging you here for visibility. The critical fix noted above is the only thing we must have for RC2. I know the rest of this is lower priority than the other work we've itemized in #4260.

[nathaniel-may]

If we're going to include log levels on the CLI (more on this below), disable duplicative WARNING prefixes in messages / formatted via warning_tag

This is a good reason why I think the warning stuff should live in the events mod eventually.

[emmyoop]

LGTM

[nathaniel-may]

let's encapsulate this into a function since it's used 3 times.

Suggested change

	log_line = (
	create_json_log_line(e, msg_fn=lambda x: x.file_msg())
	if this.format_json else
	create_text_log_line(e, msg_fn=lambda x: x.file_msg())
	)
	log_line = create_log_line(json=this.format_json, e=e, msg_fn=lambda x: x.file_msg())

where

def create_log_line(json: bool, e: T_Event, msg_fn: Callable[[T_Event], str]) -> str:
    return (
        create_json_log_line(e, msg_fn)
        if this.format_json else
        create_text_log_line(e, msg_fn)
    )

[jtcohen6]

Closing in favor of #4388