Function assigned to field should be completed as function

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### How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

### Which OS are you using?

Windows

### What is the issue affecting?

Completion

### Expected Behaviour

When providing an alias for a function in a table, the alias should be treated as a function.

### Actual Behaviour

When providing an alias for a function in a table, the alias is treated as a field and does not get completed as a function. Hover shows that the field is a function, but completion does not agree or complete with parentheses.


### Reproduction steps

1. Use the below code
```lua
---@class myTable
local t = {}

---Does a thing
---@param a integer
---@param b string
---@param c boolean
function t.myFunc(a, b, c) end
t.myAlias = t.myFunc

```
2. Try to get completions for the **function** `t.myAlias`

### Additional Notes

This would be incredibly useful for aliasing a function — something that [luassert](https://github.com/sumneko/lua-language-server/pull/1556) does **a lot**.

### Log File

_No response_

Reproduce the issue in the LuaLS Visual Studio Code extension using the provided t.myFunc and t.myAlias example, then trace the completion and type information handling for the alias. Done means t.myAlias is recognized as a function in completion, offers parentheses, and agrees with the function type shown by hover.

Written by the indexing model from the issue text.