Implement rule for unserialize

[eliashaeussler]

This PR implements a new rule for unserialize. Following behaviors will trigger an error:

• Parameter $2 options is NOT set (only with parameter checkInsecureUnserialize: true)
• Parameter $2 options has an invalid array key (neither allowed_classes nor max_depth)
• Parameter $2 options has invalid type for allowed_classes
• Parameter $2 options has 'allowed_classes' => true (only with parameter checkInsecureUnserialize: true)
• Parameter $2 options has invalid array item for allowed_classes
• Parameter $2 options has max_depth key on PHP < 7.4
• Parameter $2 options has invalid type for max_depth
• Parameter $2 options is set, but does not have allowed_classes configured (only with parameter checkInsecureUnserialize: true)