Improve utils.FatalError error formatting

[strideynet]

I've noticed the past few months a number of cases where users reporting an issue with tbot were confused by the error message output by tbot.

A contributing factor to this is that they appear "scrambled". This scrambling appears to be caused by utils.formatErrorWriter which prints the Messages from deepest to shallowest, and then prints the underlying error. But - this makes no sense - the underlying error is the deepest element. You can see an example of this below.

I noticed that when -d was provided, a different implementation was used to print the error. This implementation is within our trace package, and correctly shows the messages from shallowest to deepest - and also indents each message. This helps distinguish each message and is especially important when printing a stack including an aggregate error. So - I figured it made sense to reuse that implementation.

Example Code:

package main

import (
	"github.com/gravitational/teleport/lib/utils"
	"github.com/gravitational/trace"
)

func chargeCapacitors() error {
	return trace.BadParameter("capacitor bank exploded")
}

func prepareEnergySubsystem() error {
	return trace.Wrap(chargeCapacitors(), "charging capacitors")
}

func jumpToLightspeed() error {
	return trace.Wrap(prepareEnergySubsystem(), "preparing energy subsystem")
}

func main() {
	err := trace.Wrap(jumpToLightspeed(), "jumping to lightspeed")
	utils.FatalError(err)
}

Prior to this PR:

noah@Noahs-MBP teleport % go run ./example   
ERROR: charging capacitors
preparing energy subsystem
jumping to lightspeed
capacitor exploded

exit status 1

After this PR:

noah@Noahs-MBP teleport % go run ./example 
ERROR: jumping to lightspeed
        preparing energy subsystem
                charging capacitors
                        capacitor exploded

exit status 1

If we feel the risk this change is too wide for utils.FatalError, I'm more than happy to isolate this fix to tbot.

nb: I'm also currently investigating an issue within trace when pretty printing aggregate errors. I hope to raise a PR for that soonish as part of a general effort to improve tbot's error output.

[github-actions]

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[codingllama]

Seems reasonable to me, as is the change in error messages overall.

[public-teleport-github-review-bot]

@strideynet See the table below for backport results.

Branch	Result
branch/v12	Create PR
branch/v13	Create PR
branch/v14	Create PR