Change `AbstractAnonymizer::__construct()` signature in order to finalize `Context` implementation properly

[pounard]

In many occasions, we need to share context for a single anonyzation run between anonymizers:

• Global "salt" option, for hashing (actual).
• Global "base_path" option introduced in feature: file enum anonymizer, inject samples in database from a plain text or csv file #228 (not merged yet) for file loading.
• Future sample table list (in order to avoid creating and populating the same table many times when the same anonymizer with a fixed list is used more than once).
• And probably more in the future.

All this data must go directly to anonymizers, but using the Options instance is wrong:

• Even if we propagate some data into it, it is not shared (so goodbye sample table sharing).
• Adding more and more options into it makes anonymizers unable to use those options names for themselves.

The less impactful solution I found is the following:

1. Create a new Context class, which will carry all this information.
2. Change constructor of AbstractAnonymizer in order to accept this new parameter.

The PR #235 is a working proof of concept that introduce a new Context class in a backward compatibility fashion. If this PR is accepted, in 3.0, we will need to do the following change:

• Change AbstractAnonymizer::__construct() signature, in order to accept both Options $options and Context $context parameters.
• Remove all backward compatibility layer accordinly.
• Follow many @todo, #[\Deprecated] and associated \trigger_deprecation() calls we left in there to indicate us the right path for removal.