[perf] Speed up ReturnTypeFrom* rules by checking return shape before class method override guard

[TomasVotruba]

Performance refactor of 8 return-type-inference rules. No behavior change - all 100 fixtures pass unchanged.

Each rule bailed out via ClassMethodReturnTypeOverrideGuard::shouldSkipClassMethod() before checking the cheap structural precondition that there is a single/only return with an expression. That guard is reflection-heavy: it resolves class reflection, walks parent methods and checks type-guarded/abstract/interface state.

The cheap return-shape check (findReturnsScoped() + hasOnlyReturnWithExpr(), a local AST pass that needs no scope) is now done first, so methods that cannot match never pay for the override guard. ReturnTypeFromStrictConstantReturnRector already followed this order - the rest are aligned to it.

Rules updated:

• NumericReturnTypeFromStrictReturnsRector
• NumericReturnTypeFromStrictScalarReturnsRector
• BoolReturnTypeFromBooleanConstAndStrictReturnsRector
• BoolReturnTypeFromBooleanConstReturnsRector
• BoolReturnTypeFromBooleanStrictReturnsRector
• ReturnTypeFromMockObjectRector
• ReturnTypeFromReturnNewRector
• ReturnTypeFromStrictTypedCallRector (also moved the cheap check ahead of collectStrictReturnTypes())

Reordering is safe: all moved checks are side-effect-free bail conditions that must all pass to proceed.