[WIP] EZP-31682: Support Argon2 password hashes

[glye]

Question	Answer
JIRA issue	EZP-31682
Type	feature
Target eZ Platform version	v3.x
BC breaks	no
Tests pass	tbd
Doc needed	yes

Add support for Argon2 password hashes, which are supported in PHP 7.2 / 7.3 but optional, PHP must be compiled with support for them.
https://www.php.net/manual/en/function.password-hash.php

Out of scope: Add support for the various cost/threads options. We could add this for bcrypt too.

Checklist:

• PR description is updated.
• Tests are implemented.
• Added code follows Coding Standards (use $ composer fix-cs).
• PR is ready for a review.
• isValidPassword() also needs to check if support is compiled in, refactor to do this all in one place.

[glye]

Continued in ibexa/core#581