Fix trait insteadof + qualified as alias dropping winner method (#9903)

[PurHur]

Summary

• Fix regression where combining TA::f insteadof TB with TB::f as g dropped the winner method f from the class
• Trait-qualified Trait::method as alias now adds an alias without unsetting the merged method under the original name (matches Zend/zend_traits.c)
• Applied fix in VM (applyTraitUsesWithAdaptations), JIT trait flattening, and compile-time TraitComposedMethodResolver

Closes #9903

php-src reference

• Zend/zend_compile.c — trait alias/precedence
• Zend/zend_inheritance.c — trait method composition

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php bin/vm.php test/repro-maintainer/trait_use_adaptations.php
vendor/bin/phpunit --filter testTraitInsteadofWithTraitQualifiedAlias
vendor/bin/phpunit test/compliance/cases/language/trait_use_adaptations.phpt
'

Output:

AB
OK (1 test, 1 assertion)  # unit test
OK (1 test, 1 assertion)  # compliance phpt

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