Properties (getter/setter) support

Nobody has claimed this yet.

Lua's variables can act as C#-like properties by setting `__newindex` appropriately.

Getters and setters occasionally have different type signatures. However, the `@field` annotation can only represent one type.

```lua
-- hoge.meta.lua

---@meta

---@class Point
---@field x number
---@field y number
Point = {}

---@class Hoge
---@field position Point ⚠️ actually a property
Hoge = {}

---@return Hoge
function new_hoge() end
```

```lua
-- main.lua

local hoge = new_hoge()
hoge.position = { 3, 7 } -- emits "Missing required fields in type `Point`: `x`, `y`"
print(hoge.position.x) -- 3.0
print(hoge.position.y) -- 7.0
```

(Full sample program is [here](https://codeberg.org/haruomaki/luaproperty))

It should be annotated as "`position`'s setter receives a `table`, and its getter returns a `Point`."

How about adding a new syntax to describe this?

Start with the annotation examples in hoge.meta.lua and main.lua, then reproduce the diagnostic for assigning a table to hoge.position. The issue names no repository files or tests, so the relevant annotation and type-checking entry points must be located. Done means the annotation syntax can express distinct setter and getter types and the sample assignment no longer reports missing Point fields.

Written by the indexing model from the issue text.