[depre] Deprecate Symplify set, as mostly part of common set that have more clearer naming + remove deprecate phpunit and strict sets

[TomasVotruba]

What

Deprecate the symplify prepared set and remove the already-deprecated phpunit and strict sets.

• symplify — soft-deprecated. Its rules were duplicates of the common sets under less clear names. The rules now live in common (array, docblock, spaces). Passing symplify: true now triggers an E_USER_DEPRECATED warning and no longer loads the set.
• phpunit — removed. It was dangerous to run without proper context. Use Rector instead.
• strict — removed. Same reason — dangerous without context. Use Rector instead.
• SetList::PHPUNIT and SetList::STRICT constants removed; SetList::SYMPLIFY marked @deprecated.
• Dropped unused packages/coding-standard/config/symplify.php; narrowed config/set/symplify.php.

How to update your ecs.php

Drop the deprecated flags. The annotation/spacing/strict-types rules they covered are now in the common sets — enable common: true (or the matching with*Level() methods).

 use Symplify\EasyCodingStandard\Config\ECSConfig;

 return ECSConfig::configure()
     ->withPreparedSets(
         common: true,
-        symplify: true,
-        phpunit: true,
-        strict: true,
     )
     ->withRules([
         // ...
     ]);

If you still need strict-types or PHPUnit-specific transforms, move them to Rector where they run with proper context.