[11.x] Str trim methods

[patrickomeara]

The native methods trim(), ltrim() and rtrim() don't remove the unicode whitecode character NBSP.

Str::squish() removes these characters, as does TrimStrings middleware.

This PR adds trim(), ltrim() and rtrim() static methods to the Str helper, and also uses these methods in the corresponding Stringable calls.

Note: For reviewers the whitespace characters don't show up in the web UI.

Test screenshots attached to show them.

[patrickomeara]

An update here. The TrimStrings middleware handles binary data by using the native method when preg_replace returns null. I have implemented this behaviour in the new methods and also added the changes from @dasundev's #50832

[taylorotwell]

@patrickomeara why is the white space removed by trim different from the regex used by ltrim and rtrim?

[patrickomeara]

@taylorotwell The whitespace characters are the same, ltrim removes it from the beginning ^, and rtrim from the end $

[taylorotwell]

Got it. Thanks!