Function modifier rework

[Efnilite]

Problem

Parameter modifiers previously did not have proper support for containing data within a modifier, requiring messy code to make it work. Additionally, modifiers that defined constraints (such as RangedModifier) required internal changes to check values, thereby not allowing any addon from registering a custom modifier.

Signature modifiers, such as a function being local or returning a value, were previously dictated by fields in the Signature class. To allow for easier future expansion, signature modifiers have been migrated to use the same system as parameter modifiers.

Solution

Parameters

• Added support for custom modifiers.
• Made modifiers instances instead of static variables. This allows each instance to contain data specific to the function.
• Added support for Constraint parameter modifiers, which check parameter values and deny function execution if a parameter value is invalid.

Signature

• Added support for custom modifiers.
• Added custom modifiers to DefaultFunction builder.

Priority

• Added isBefore, isEqual, isAfter for simpler priority comparisons.

Parameters.java

• Updated for future PRs.

Testing Completed

Added ParameterTest and SignatureTest for testing toFormattedString, and existing tests.

Supporting Information

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Completes: none
Related: #8657
AI assistance: none

[sovdeeth]

why do we have 2 modifier interfaces now? Can't they be unified? idk it seems a bit confusing to have these duplicated

[Efnilite]

the modifiers mentioned here are applicable to function signatures (e.g. local or async). the other modifiers are for parameters (e.g. optional, keyed). i don't think it makes sense to merge them, since additional checks would be required to determine whether any given modifier is applicable to a signature or a parameter. do you think it could be useful to have a unified interface for modifiers that feature the priority and toFormattedString functions?

also, referencing these two modifiers is done through Signature.Modifier and Parameter.Modifier. do you want me to rename them to something clearer?