This adds the ability to enable dropdown options only if certain conditions are met. It uses the same condition API as conditional groups, so it's quite powerful.

Changes:

• Moved Condition class and familiars into its own file.
• Add optional condition key to DropDownOption.
• Add conditions: dict[T, Condition] parameter to EnumInput. This makes it easy to define option conditions.
• Add Dropdown.wrap_with_conditional_group(). This function essentially adds a conditional group around the dropdown with its options are conditions. The basic idea is that if none of the options have their conditions met, then the dropdown is effectively disabled since you cannot input a value. wrap_with_conditional_group adds a conditional group that hides the dropdown if this is the case.
• Generally improved the condition API in the frontend.
• Changed when enum conditions are considered to be fulfilled. It now requires the value of the enum to match and the conditions of the enum input to match. The idea is that an enum value is only valid if the enum is visible/enabled.