Allow PHP CS Fixer as pipeline step for stdin -> format -> stdout

Feature request

Step 1

document existing handling of STDIN, example of ./php-cs-fixer fix - < src/WordMatcher.php

Step 2

Introduce new behaviour for handling STDIN:

• introduce new --format option called raw (or provide better name), that will produce raw, full file to STDOUT
• use newly introduced format as default when working with STDIN, if env var PHP_CS_FIXER_FUTURE_MODE=1 is configured (to not cause any BC for current Major)
• raise error if --format=raw is used for non-STDIN mode

Link to Discussion where feature request was formed

https://github.com/PHP-CS-Fixer/PHP-CS-Fixer/discussions/8309