Added Phalcon\Security\Random:base62

[sergeyklay]

Hello!

• Type: new feature
• Link to issue: [3.x] [NFR] - Add Base 62 to Phalcon\Security\Random #12105

In raising this pull request, I confirm the following:

• I have read and understood the Contributing Guidelines?
• I have checked that another pull request for this purpose does not exist.
• I wrote some tests for this PR.

Small description of change: Added Phalcon\Security\Random:base62 to provide the largest value that can safely be used in URLs without needing to take extra characters into consideration.

use Phalcon\Security\Random;

$random = new Random();

// Random base62 string
echo $random->base62(); // z0RkwHfh8ErDM1xw

Thanks