AOT: fix request_parse_body compile/link (#5965)

[PurHur]

Summary

• Fix LLVM dominance for list-unpack-style $post = $pair[0] after request_parse_body() by promoting assign targets to entry allocas
• Link standalone putenv() through EnvLocalRuntime (__compiler_env_register_putenv) without nested-JIT HashTable::update breakage
• Route GetenvJitHelper hashtable population through phpc_native_ht_set_string_key (php-in-PHP, no C runtime growth)
• Preserve LLVM insert blocks across RequestParseBodyRuntime / EnvLocalRuntime nested helper emits

Verification

source script/php-env.sh
export PHP_COMPILER_PROFILE=8.4
php bin/compile.php -o /tmp/rpb test/fixtures/aot/cases/request_parse_body_urlencoded.phpt
echo compile:$?   # 0 (link OK)
/tmp/rpb          # segfault exit 139 at c:main_before_php — runtime follow-up
vendor/bin/phpunit test/aot/AotTest.php --filter request_parse
# compile/link passes; run assertions fail on segfault (exit 139/134)

Closes #5965 when runtime segfault is fixed.

Made with Cursor

[PurHur]

Maintainer triage 2026-07-08: compile/link green per PR body but AOT runtime still segfaults at c:main_before_php — not merge-ready until execute repro passes. Re-run bootstrap not required (stdlib/AOT path only).

[PurHur]

Maintainer triage 2026-07-08: compile/link green per PR body but runtime segfault remains — hold merge until AOT execute passes issue repro.