[12.x] Preserve item types (object or array) when using Arr::select() or Collection::select()

[Icexist]

This PR proposes a change to maintain the type of an array or collection value upon return from the select method.

Existing behavior converts all values returned from select as arrays.

---

10.44.0 added the Collection::select() and Arr::select() methods #49845 and 10.45.0 updated it to work with ArrayAccess #50072

However, these convert any item in either an array or the Collection into an array even if it is an object. See https://github.com/laravel/framework/blob/master/src/Illuminate/Collections/Arr.php#L532-L533

For example, if you have an array of objects and select a single column, it will become an array of arrays.

$obj1 = new \stdClass;
$obj1->color = 'blue';
$obj1->temperature = 'warm';

$obj2 = new \stdClass;
$obj2->color = 'green';
$obj2->temperature = 'cool';

$arr = [$obj1, $obj2];

$selected = Arr::select($arr, 'color');
/* 
[
    [ 'color' => 'blue' ],
    [ 'color' => 'green' ],
]
*/

This is unexpected behavior as the Collection returned from Query Builder has each row of data represented as a stdClass object. Using select on that Collection then converts all the stdClass objects to array types, breaking downstream code.

The proposed change would coerce the individual value of the Collection or Array back into an object if the value was originally an object.

Previously #50749 as a change to 11.x.

[taylorotwell]

This would be a breaking change to apps that are working around this.

[decadence]

Title is wrong. It's for master, not for 11.x

[Icexist]

I agree, but @driesvints changed it so I'm reluctant to switch it back. Especially after Taylor closed it.