[CodeQuality] Skip WillReturnCallbackFallbackToReturnFalseRector when closure ends in throw or never-returning call

[TomasVotruba]

Fixes rectorphp/rector#9931

WillReturnCallbackFallbackToReturnFalseRector appended a return false; fallback even when the willReturnCallback() closure could not fall through - it ended in a throw or in a call to a method that returns never (e.g. self::fail()). The added statement was dead code.

The fallthrough check only bailed on a trailing Return_. It now also bails when the last statement is a throw, or an expression whose native type is never.

Covered by two skip fixtures matching the reported cases.

[TomasVotruba]

Already fixed