Add php-cs-fixer config and reformat

The formatting in this project has become something of a mess,
because it changed over time. Add a CS fixer config and reformat
to the desired st

Add php-cs-fixer config and reformat

The formatting in this project has become something of a mess,
because it changed over time. Add a CS fixer config and reformat
to the desired style, which is PSR-12, but with sane brace placement.

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Add PhpVersion class

Use PHP 8.0 token representation

Migrate everything to use PhpToken-compatible token representation,
rather than the legacy array/string representation.

Correctly handle ?-> in encapsed strings

Followup upstream change.

Handle flexible heredoc via TokenEmulator

Extend the interface to support preprocessing.

Add support for nullsafe operator