Go-to-def should include both declaration(s) and target call signature

[ahejlsberg]

Fixes #1528.

[Copilot]

Pull Request Overview

This pull request improves the "Go to Definition" functionality by ensuring that both general declarations and specific call signatures are included in the results. When a call signature can be resolved, it replaces function-like declarations while preserving non-function declarations.

• Refactored the definition resolution logic to extract it into a reusable function
• Modified the signature handling to include both general declarations and specific call signatures
• Simplified the location creation logic by removing body-based filtering

[Copilot]

Using slices.Clip(declarations) creates an unnecessary copy of the slice. Since core.Filter likely creates a new slice anyway, you can pass declarations directly to avoid the extra allocation.

Suggested change

	nonFunctionDeclarations := core.Filter(slices.Clip(declarations), func(node *ast.Node) bool { return !ast.IsFunctionLike(node) })
	nonFunctionDeclarations := core.Filter(declarations, func(node *ast.Node) bool { return !ast.IsFunctionLike(node) })

[ahejlsberg]

core.Filter only creates a new slice if something was removed. Thus the need for slices.Clip.