[Enhancement] Improve fun type matching

[d-enk]

---@class Class
---@field f fun(s: string): integer

---@param f fun(x: string): integer
local function handle(f)
	return f("string")
end

-----

---@param i number
---@return boolean
local function is_positive(i)
	return i >= 0
end

handle(is_positive) -- expect `param-type-mismatch`

---@type Class
local _ = { f = is_positive } -- expect `assign-type-mismatch`

Expected warning:
Type fun(i: number):boolean cannot match fun(x: string):integer

I didn't find duplicates, although I expected them
maybe I didn't search well

[tomlau10]

similar issue: #2702