revive: improve 'exported' rule output.

[ldez]

Fixes #1993

example.go

package main

import "fmt"

var HorribleGlobalVar = map[int]string{
	1:    "s1",
	2:    "s2",
	3:    "s3",
	2000: "s2000",
}

var (
	GroupOfHorribleGlobalVar = map[int]string{
		1:    "s1",
		2:    "s2",
		3:    "s3",
		2000: "s2000",
	}
)

type Foo struct {
	S1 string
	S2 string
	S3 string
	S4 string
	S5 string
}

func Goo() {
	to := "test"

	fmt.Println(to)
}

.golangci.yml

linters:

  disable-all: true
  enable:
    - revive

issues:
  exclude-use-default: false

before the PR

$ golangci-lint run --disable-all -Erevive
main.go:5:5: exported: exported var HorribleGlobalVar should have comment or be unexported (revive)
var HorribleGlobalVar = map[int]string{
        1:    "s1",
        2:    "s2",
        3:    "s3",
        2000: "s2000",
}
main.go:13:2: exported: exported var GroupOfHorribleGlobalVar should have comment or be unexported (revive)
        GroupOfHorribleGlobalVar = map[int]string{
                1:    "s1",
                2:    "s2",
                3:    "s3",
                2000: "s2000",
        }
main.go:21:6: exported: exported type Foo should have comment or be unexported (revive)
type Foo struct {
        S1 string
        S2 string
        S3 string
        S4 string
        S5 string
}
main.go:29:1: exported: exported function Goo should have comment or be unexported (revive)
func Goo() {
        to := "test"

        fmt.Println(to)
}

with the PR

$ ./golangci-lint run --disable-all -Erevive
main.go:5:5: exported: exported var HorribleGlobalVar should have comment or be unexported (revive)
var HorribleGlobalVar = map[int]string{
    ^
main.go:13:2: exported: exported var GroupOfHorribleGlobalVar should have comment or be unexported (revive)
        GroupOfHorribleGlobalVar = map[int]string{
        ^
main.go:21:6: exported: exported type Foo should have comment or be unexported (revive)
type Foo struct {
     ^
main.go:29:1: exported: exported function Goo should have comment or be unexported (revive)
func Goo() {
^