fix(compiler): infer static return type for uniform match expressions

[prateekbhujel]

Summary

This PR adds static type inference for PHP match expressions when all non-throwing arms evaluate to the same uniform type (such as int, float, bool, string, etc.).

Problem

Previously, Expr\Match_ was absent from CompilerBase::detectTypeOfExpr(), defaulting all match expressions to Type::VAR (php::Var).
Even when every arm returned a known primitive (e.g. match ($x) { 1 => 10, 2 => 20, default => 30 } in a function returning : int):

1. The emitted lambda returned php::Var, boxing every return value into a Zend Variant.
2. A runtime return type check php::throwReturnTypeError() was emitted at the function exit.
3. An unboxing call (php::toInt(), etc.) was required.
4. Local variable assignments ($val = match (...)) forced the variable storage to php::Var.

Changes

1. CompilerBase::detectTypeOfExpr():
   • Added case 'Expr_Match': aggregates the types of all non-throwing arm bodies.
   • If all non-throwing arms evaluate to a single unique type, that static type is returned.
   • Falls back to Type::VAR if types are mixed or dynamic.
2. SelectionExpressionTrait::parseMatch():
   • Computes $returnType using detectTypeOfExpr() / getNormalAssignType().
   • Tags the AST node with ATTR_LOWERED_TYPE.
   • For non-default cases without a match, emits php::throwException("UnhandledMatchError", ...); return {}; for typed lambdas.
3. SelectionExpressionTrait::formatMatchReturn():
   • Handles Expr\Throw_ arms without attempting to return php::throwException() as an unconvertible primitive value.
   • Allocates temporary variables matching $returnType when after-statements are present.
4. Tests:
   • Added MatchExpressionCodegenTest and fixture match-expression-codegen.php verifying typed lambda signatures, avoidance of redundant runtime return type checks, throw arm handling, and local variable type inference.