[PHP] PHP 8.0 updates (sublimehq#2275)

* [PHP] Add some built-in classes and constants

Classes:

ArgumentCountError
ArithmeticError
CompileError
DivisionByZeroError
Error
ParseError
Stringable
TypeError
ValueError
WeakMap
WeakReference

---

Constants:

FILTER_VALIDATE_BOOL

---

https://github.com/symfony/polyfill-php80
https://wiki.php.net/rfc/stringable
https://wiki.php.net/rfc/weak_maps
https://www.php.net/manual/en/reserved.exceptions.php
https://www.php.net/manual/en/spl.exceptions.php

* [PHP] Add support for union types

https://wiki.php.net/rfc/union_types_v2

* [PHP] Add support for "static" return type

https://wiki.php.net/rfc/static_return_type

* [PHP] Add core function: str_contains

https://wiki.php.net/rfc/str_contains

* [PHP] Add core function: get_debug_type

* [PHP] Add built-in class: DateTimeImmutable, DateTimeInterface

* [PHP] Add core function: fdiv

php/php-src#4769

* [PHP] Add built-in class: PhpToken

https://wiki.php.net/rfc/token_as_object

* [PHP] Add core function: str_starts_with, str_ends_with

https://wiki.php.net/rfc/add_str_starts_with_and_ends_with_functions

* [PHP] Add support for short attributes ("@@")

https://wiki.php.net/rfc/attributes_v2
https://wiki.php.net/rfc/attribute_amendments
https://wiki.php.net/rfc/shorter_attribute_syntax

* [PHP] Add support for "mixed" type hinting

https://wiki.php.net/rfc/mixed_type_v2

* [PHP] Add support for constructor property promotion

https://wiki.php.net/rfc/constructor_promotion

* [PHP] Extract visibility modifier as a variable

* [PHP] Add missing constant: DNS_CAA

Fixes sublimehq#991

* [PHP] Add support for "match" expression

https://wiki.php.net/rfc/match_expression_v2

* [PHP] Add snippet: fn ...

* [PHP] Add snippet: match ...

* [PHP] Add support for named arguments

https://wiki.php.net/rfc/named_params

* [PHP] Add support for nullsafe operator

https://wiki.php.net/rfc/nullsafe_operator

* [PHP] Add core function: get_resource_id

php/php-src#5427

* [PHP] Add built-in class: InternalIterator

php/php-src#5216

* [PHP] Syntax definition use "version: 2"

* [PHP] Fix punctuation scopes have no begin/end