Add support for marking custom functions as deprecated with visual warnings

[danvervlad]

Summary

• Adds the ability to mark actions, conditions, and expressions as deprecated in extension functions
• Displays visual deprecation warnings in the Events Sheet when deprecated functions are used
• Allows extension authors to provide a deprecation message explaining what to use instead

Changes

Core/GDCore:

• Added SetDeprecationMessage and IsDeprecated methods to InstructionMetadata, ExpressionMetadata, and MultipleInstructionMetadata
• Added DeprecatedExpression error type to ExpressionParserError
• Extended InstructionValidator with ValidateParameter that returns both validity and deprecation status via new ParameterValidationResult struct
• Added deprecation fields to EventsFunction model (isDeprecated, deprecationMessage)

Events Sheet (UI):

• Displays [DEPRECATED] prefix for deprecated actions and conditions
• Shows deprecation message in tooltips
• Highlights deprecated expressions with visual styling (background highlight)
• Respects the existing showDeprecatedInstructionWarning preference flag

Extension Editor:

• Added "Deprecated" checkbox in function properties
• Added "Deprecation message" text field when function is marked deprecated

[danvervlad]

Function properties

With Deprecated = true

With Deprecated = false

With Show a warning on deprecated actions and conditions = true

In event sheet

In action/condition details

In expression details

With Show a warning on deprecated actions and conditions = false

In event sheet

In action/condition details

In expression details

[danvervlad]

In extension json, for serialization