Language: BackedEnum::from() / tryFrom() (#3114)

[PurHur]

Summary

VM lowering for backed enum ::from() and ::tryFrom() with case lookup by backing value (Zend zend_enum.c parity).

• BackedEnum::caseForValue() iterates ClassEntry::enumCases[] with int/string backing coercion
• EnumFromHandler internal builtin dispatched from initStaticCallable
• ValueError / TypeError bridged into user catch via executeInternalHandler (Runtime: intdiv() division by zero — void context silent + uncatchable in try/catch (Zend zend_exceptions.c parity) #3648)
• Compliance PHPTs + VmEnumFromTest (string + int backed, invalid value, caught/uncaught paths)
• Enum parser patch guard in apply-patches.sh when patch already applied

php-src reference

• Zend/zend_enum.c — zend_enum_from_case(), zend_try_enum_from_case()
• Zend/zend_interfaces.c — BackedEnum internal API

Verification

# Issue repro
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/vm.php -r '"'"'enum Color: string { case Red = "red"; case Blue = "blue"; } echo Color::from("red")->name; echo Color::tryFrom("nope") === null ? "null" : "bad";'"'"''
# Rednull

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit test/unit/VmEnumFromTest.php test/compliance/EnumVMTest.php --filter "VmEnumFrom|enum_from|enum_try_from"'
# OK (8 tests)

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit test/unit/VmEnumBasicTest.php test/compliance/EnumVMTest.php --filter enum_basic'
# OK — no regression

Note: enum_instanceof.phpt failure is pre-existing on master (#3550), unrelated to this PR. JIT deferred per issue scope.

Closes #3114

[PurHur]

Maintainer local verify (Docker docker-exec, master base + PR branch)

vendor/bin/phpunit --filter VmEnumFromTest on PR head errors (0 assertions):

TypeError: PHPCfg\Op\Stmt\Enum_::__construct(): Argument #3 ($implements) must be of type array, PHPCfg\Block given

Looks like php-cfg Parser enum path vs Enum_ ctor mismatch in the container’s vendor tree — please confirm composer install + patches on the branch and that unit tests pass with:

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter VmEnumFromTest'

Not merging until green; VM compliance enum_from phpt path is the issue repro from the PR body.