Support attributes v2 RFC when syntax is finalized

[TysonAndre]

https://externals.io/message/110217 [RFC] Amendments to Attributes is proposing changing the final syntax

https://wiki.php.net/rfc/attributes_v2 is in the voting phase - there are currently 48 yes votes and 1 no vote, and <<Attribute(optional arg list)>> is the preferred syntax.

This RFC proposes Attributes as a form of structured, syntactic metadata to declarations of classes, properties, functions, methods, parameters and constants.

Relevant parts of the CFG in the implementation PR in Zend/zend_language_parser.y

attribute_arguments:
		expr
			{ $$ = zend_ast_create_list(1, ZEND_AST_ARG_LIST, $1); }
	|	attribute_arguments ',' expr
			{ $$ = zend_ast_list_add($1, $3); }
;

attribute_decl:
		class_name_reference
			{ $$ = zend_ast_create(ZEND_AST_ATTRIBUTE, $1, NULL); }
	|	class_name_reference '(' ')'
			{ $$ = zend_ast_create(ZEND_AST_ATTRIBUTE, $1, NULL); }
	|	class_name_reference '(' attribute_arguments ')'
			{ $$ = zend_ast_create(ZEND_AST_ATTRIBUTE, $1, $3); }
;

attribute:
		T_SL attribute_decl T_SR	{ $$ = $2; }
;

attributes:
		attribute				{ $$ = zend_ast_create_list(1, ZEND_AST_ATTRIBUTE_LIST, $1); }
	|	attributes attribute	{ $$ = zend_ast_list_add($1, $2); }
;