refactor: replace multierror with native errors (#159)

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## What does this PR do?

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## Why is it important?

Go 1.20 added support for wrapping multiple errors. Drop multierror
library and use stdlib errors

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## Related issues

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-

go.mod

@@ -11,7 +11,6 @@ require (
 	github.com/elastic/go-windows v1.0.1
 	github.com/elastic/gosigar v0.14.2
 	github.com/gofrs/uuid v4.4.0+incompatible
-	github.com/joeshaw/multierror v0.0.0-20140124173710-69b34d4ec901
 	github.com/magefile/mage v1.15.0
 	github.com/shirou/gopsutil/v3 v3.21.12
 	github.com/stretchr/testify v1.9.0

go.sum

@@ -49,8 +49,6 @@ github.com/google/licenseclassifier v0.0.0-20200402202327-879cb1424de0/go.mod h1
 github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
 github.com/jessevdk/go-flags v1.4.0/go.mod h1:4FA24M0QyGHXBuZZK/XkWh8h0e1EYbRYJSGM75WSRxI=
-github.com/joeshaw/multierror v0.0.0-20140124173710-69b34d4ec901 h1:rp+c0RAYOWj8l6qbCUTSiRLG/iKnW3K3/QfPPuSsBt4=
-github.com/joeshaw/multierror v0.0.0-20140124173710-69b34d4ec901/go.mod h1:Z86h9688Y0wesXCyonoVr47MasHilkuLMqGhRZ4Hpak=
 github.com/karrick/godirwalk v1.15.6/go.mod h1:j4mkqPuvaLI8mp1DroR3P6ad7cyYd4c1qeJ3RV7ULlk=
 github.com/karrick/godirwalk v1.15.8 h1:7+rWAZPn9zuRxaIqqT8Ohs2Q2Ac0msBqwRdxNCr2VVs=
 github.com/karrick/godirwalk v1.15.8/go.mod h1:j4mkqPuvaLI8mp1DroR3P6ad7cyYd4c1qeJ3RV7ULlk=

metric/cpu/metrics_freebsd.go

@@ -19,11 +19,10 @@ package cpu
 
 import (
 	"bufio"
+	"errors"
 	"fmt"
 	"strings"
 
-	"github.com/joeshaw/multierror"
-
 	"github.com/elastic/elastic-agent-libs/opt"
 )
 
@@ -38,7 +37,7 @@ func scanStatFile(scanner *bufio.Scanner) (CPUMetrics, error) {
 func parseCPULine(line string) (CPU, error) {
 	cpuData := CPU{}
 	fields := strings.Fields(line)
-	var errs multierror.Errors
+	var errs []error
 
 	tryParseUint := func(name, field string) (v opt.Uint) {
 		u, err := touint(field)
@@ -55,5 +54,5 @@ func parseCPULine(line string) (CPU, error) {
 	cpuData.Sys = tryParseUint("sys", fields[3])
 	cpuData.Idle = tryParseUint("idle", fields[4])
 
-	return cpuData, errs.Err()
+	return cpuData, errors.Join(errs...)
 }

metric/cpu/metrics_linux.go

@@ -19,11 +19,10 @@ package cpu
 
 import (
 	"bufio"
+	"errors"
 	"fmt"
 	"strings"
 
-	"github.com/joeshaw/multierror"
-
 	"github.com/elastic/elastic-agent-libs/opt"
 )
 
@@ -37,7 +36,7 @@ func scanStatFile(scanner *bufio.Scanner) (CPUMetrics, error) {
 
 func parseCPULine(line string) (CPU, error) {
 
-	var errs multierror.Errors
+	var errs []error
 	tryParseUint := func(name, field string) (v opt.Uint) {
 		u, err := touint(field)
 		if err != nil {
@@ -60,7 +59,7 @@ func parseCPULine(line string) (CPU, error) {
 	cpuData.SoftIrq = tryParseUint("softirq", fields[7])
 	cpuData.Stolen = tryParseUint("stolen", fields[8])
 
-	return cpuData, errs.Err()
+	return cpuData, errors.Join(errs...)
 }
 
 func scanCPUInfoFile(scanner *bufio.Scanner) ([]CPUInfo, error) {