[5.3] Make str_replace_array() not interpret needle as a regex

[vlakoff]

• Targetting 5.3 as it's a breaking change. See vlakoff@3db6f2a.
• Also adding a Str::replaceArray method for codebase consistency.

[GrahamCampbell]

Please don't align.

[vlakoff]

This would reduce consistency with the rest of Str.php and helpers.php files.
I think it would be better to change code style in whole files at once, and in a dedicated commit.

[taylorotwell]

Needs full description of purpose of this change, what it does, what it fixes, purpose for existing, etc.

[vlakoff]

My guess is that when you implemented this function (in ab0fa95) you just thought "it's handled as a regex, but what's the big deal?".

There was a similar situation with Str::is, fixed in a294377.

There is kind of a convention, that PHP functions str_*() deal with strings, preg_*() deal with regexes. I think deviating from this convention is rather confusing.