util: faulty inspect output

Version: all
Platform: all
Subsystem: util

const a = []
a["00"] = true
Object.keys(a)
// [ '00' ]
util.inspect(a)
// Node.js < 8.4 will log
// '[  ]'
// Node.js 8.4 and master will log
// '[ true ]'
// It should be
// '[ \'00\': true ]'

This will be fixed by #14881

Btw, not sure whether your patch will fix this as well, but on master:

> a = []
[]
> a[10000000000000] = true // not a valid array index
true
> a
[  ]
> a[0] = true
true
> a
[ true ]
> a[10] = true
true
> a
[ true, <9 empty items>, true, <9999999999989 empty items>, true ]

This is the output with my patch. It is better but still not correct. I add a patch for that as well.

> a = []
[]
> a[10000000000000] = true // not a valid array index
true
> a
[ '10000000000000': true ]
> a[0] = true
true
> a
[ true, '10000000000000': true ]
> a[10] = true
true
> a
[ true, <9 empty items>, true, <9999999999989 empty items>, true ]

util: refactor inspect for performance