[11.x] Add optional ability to array wrap associative arrays

[ctwillie]

These additions allow array wrapping for associative arrays. Currently, Arr::wrap() does not wrap an associative array, but simply returns that same array. This feature is fully backwards compatible because the wrapping of associative arrays is opt in.. by passing true to Arr::wrap as the $wrapIfAssoc argument. This defaults to false which maintains current wrapping behavior.

Use Case

Functions that define an array parameter could be passed a list or an associative array. Also, many users implement functions that could be used on 1 data set or many data sets.. i.e. associative arrays. Being able to wrap associative arrays produces slightly more concise code and convenience.

Here, $params could either be ['id' => 1] or [['id' => 1], ['id' => 2]]...

Before

function (array $params) {
    $params = array_is_list($params) ? $params : [$params];

    foreach ($params as $param) {
        // process param
    }
}

After

function (array $params) {
    foreach (Arr::wrap($params, true) as $param) {
        // process param
    }
}

[taylorotwell]

Thanks for your pull request to Laravel!

Unfortunately, I'm going to delay merging this code for now. To preserve our ability to adequately maintain the framework, we need to be very careful regarding the amount of code we include.

If applicable, please consider releasing your code as a package so that the community can still take advantage of your contributions!