[CodingStyle] Deprecate StaticClosureRector and StaticArrowFunctionRector

[TomasVotruba]

What

Deprecate StaticClosureRector and StaticArrowFunctionRector.

Both rules add the static keyword to closures / arrow functions when they don't reference $this:

// before
$fn = function () { return 1; };
$arrow = fn (): string => 'test';

// after
$fn = static function () { return 1; };
$arrow = static fn (): string => 'test';

Why

• Noisy, low value. The change touches almost every closure in a codebase, producing large diffs that bury the changes that actually matter during review.
• No real-world benefit. Marking a closure static only prevents $this binding; it has no meaningful performance or correctness impact for typical code. It's a stylistic preference, not a fix.
• Better left manual. Where a static closure is genuinely wanted, it's a one-line local decision - not something worth automating across a whole project