Refactor #format_script

The `format_script` method is nearly impossible to understand or change. `def_static_method` generates 2^7 (128) `format_script` methods of the styles `format_script_true_false_true_false_true_false_true`. `static_method` is then used to build the method name from the options.

The proposed change converts `format_script` into a normal method, removes the entire `StaticConditionalContext` class, which is not used by anything else. I cannot imagine anyone is using it.

The original commit was intended to speed things up. We should be able to debug and clean up other things in this method now that it's readable.

The original commit where this style was introduced was over 5 years ago: https://github.com/haml/haml/commit/addaa09a99bd0798