php-in-php: route JIT hash_equals through HashEqualsJitHelper PHP (#9164)

[PurHur]

Summary

• Add ext/standard/HashEqualsJitHelper.php delegating to VmHash::equals() (php-src: ext/hash/hash.c)
• Replace lib/JIT/Builtin/StringHashEquals.php timing-safe compare LLVM loop (~90 lines) with thin JIT bridge
• LLVM shrink: StringHashEquals.php 125 → 109 lines; removed hash_equals_loop_* / stringData LLVM

Partial progress on #9164 (hash() / hash_hmac() LLVM migration remains open).

php-src reference

• ext/hash/hash.c — timing-safe compare for hash_equals()
• PHP SSOT: ext/standard/VmHash.php via HashEqualsJitHelper.php

Verification

vendor/bin/phpunit test/unit/StringHashEqualsRuntimeShrinkTest.php
# OK (3 tests, 9 assertions)

php bin/vm.php -r 'var_export(hash_equals("abc","abc"));'
# true

php bin/jit.php -r 'var_export(hash_equals("abc","abd"));'
# false

make bootstrap-selfhost-vm-driver-execute-probe
# bootstrap-selfhost-vm-driver-execute-probe: OK

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