[CodingStyle] Deprecate ArraySpreadInsteadOfArrayMergeRector

[TomasVotruba]

This rule caused troubles as far as I can remember. Also, it makes code harder to read in half of the cases.
Not a rule we can apply generaly.

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Deprecates ArraySpreadInsteadOfArrayMergeRector.

The rule turns readable array_merge() calls into spread arrays. That is a personal preference, not a fix: the result is harder to read and the ... in the middle of an array literal looks dangerous to reviewers.

-$values = array_merge($firstValues, $secondValues);
+$values = [...$firstValues, ...$secondValues];

The rule was not part of any set or level, so nothing else changes. It now implements DeprecatedInterface and throws on use; its tests and fixtures are removed.

[simonschaufi]

People have to get used to newer PHP syntax sooner or later. PHP 8.5 introduces the pipe operator |> and PHP 8.6 continues in that direction with placement markers ?. You personally may not like this direction but this is how PHP evolves and this is the fancy new php code style that is the future:

$uniqueEmails = $userRepository->findAll()
|> array_filter(?, fn($u) => $u->isActive())
|> array_map(fn($u) => $u->getEmail(), ?)
|> array_map(strtolower(...), ?)
|> array_unique(...);

array_merge is slow and the spread operator is the better way to use so I'm sad this rule got deprecated.

[TomasVotruba]

Pipe operators have also drawbacks based on PHP version - https://stitcher.io/blog/php-86-partial-function-application, so they should be used willingly. Same was for spread operator ... that handles keys different in 2 PHP versions. Very dangerous for projects that are not on latest version yet. Feel free to make custom rule to handle spread within pipes.