[9.x] Add String::squish() helper

[dwightwatson]

This proposes a new string helper method called squish, which is named similarly to the one in Rails. I know there's a lot of fair scrutiny given to adding new helpers but felt it was worth putting it out there in case you saw the usefulness that I do.

My use-cases are both when outputting user input that had additional unnecessary whitespace, and also when creating interpolated strings that have optional values (i.e. "A {$description} listing has been created."). In both of these instances using squish would make the content appear more professional.

If you do like this addition I can follow-up and add it to Stringable as well.

[dwightwatson]

Looks like that failing build may not be my fault 🤞

[derekmd]

You can try force-pushing your branch to re-trigger GitHub Actions and get all-green.

A recent merged PR can cause CacheFileStoreTest@testIncrementDoesNotExtendCacheLife() to intermittently fail if the second clock ticks over mid-case: #40790 (comment)

[taylorotwell]

Can you also add it to fluent strings?

[dwightwatson]

Of course, added to Stringable as well.

[rcerljenko]

@dwightwatson could the replacement param be passed as second argument like this:

public static function squish($value, $replacement = ' ')
{
    return preg_replace('/\s+/', $replacement, trim($value));
}