Bugfixes 🐛

• Fixed /** @phpstan-ignore-line */ and /** @phpstan-ignore-next-line */ annotations sometimes not working because of AST (phpstan/phpstan-src@9474696), #4750, #4759, #3834, #3563, #4250, #4798
• Do not report non-existent function after function_exists() check (phpstan/phpstan-src@28e8c11), #3576
• Make function_exists() similar to is_callable() (phpstan/phpstan-src@4a98863), #1849