JIT: list destruct MCJIT — getMessage catch lowering (#4531)

[PurHur]

Summary

• Adds ExceptionGetMessage JIT proxy (exception::getmessage) so catch arms can call $e->getMessage() when compiling list-destruct TypeError tests (Language: list/array destructuring from string — must TypeError not null slots (zend_execute.c) #7461 / Language: list destructuring JIT/MCJIT execute — phase 2 of #4308 / #4325 (zend_execute.c) #4531).
• Normalizes empty catch-variable userType in initJitMethodCall() and routes unresolved getMessage() through the Exception proxy.
• Aligns StringFsGlobVecJit / StringDirJit libc signatures with LibcExtern i8* params.
• Routes ListDestruct*Jit* unit probes through bin/jit.php subprocess (CI: Run JIT compliance tests in CI (fix LLVM skip in PHPUnit) #98 pattern); un-skips JITTest list_destructure_null / list_destructure_string compliance cases.
• Adds test/repro/list_destruct_string_typeerror.php repro script.

Verification

# VM parity — green
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit test/compliance/VMTest.php --filter list_destructure'
# OK (7 tests)

# JIT compliance (bin/jit.php) — green after un-skip
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit test/compliance/JITTest.php --filter list_destructure'
# OK (5 tests)

# List destruct JIT unit probes (bin/jit.php subprocess)
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter ListDestructNullJitCompileTest'
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter ListDestructStringJitCompileTest'
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter ListDestructNullJitExecuteTest'
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter ListDestructStringJitExecuteTest'
# OK (4 tests)

# Repro scripts (no segfault; output matches Zend)
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/jit.php test/repro/list_destruct_null_4325.php'
# a=NULL b=NULL / x=NULL / y=NULL
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/jit.php test/repro/list_destruct_string_typeerror.php'
# TypeError: Cannot use string as array (×2)

Closes #4531